Mutants & Masterminds
Suggesting this for a few reasons, which I'll sum up below. Mutants&Masterminds is a very open game focused on modern day superheroes fighting supervillains. I've some experience running the game in both its traditional superhero style and a homebrew fantasy mode. It's one of my favorite games to run both with highly creative and with very new players.
Handlings small groups
While M&M suggests some kind of team to play with, it handles pretty well even with only 1 or 2 players. The mechanics are very forgiving of bad rolls, high power players vs low power mooks works quite well, which means even a single hero can take on a squad of goons, and the setting itself generally says that heroes don´t die, they are merely defeated. So even if everything goes to hell, the players will just wake up in the villains deathtrap, ready for a daring escape, rather than dead.
The setting is modern day superheroes like the Justice League and stuff. Each player runs a superhero, and they can be built any way the player wants. The game comes with a whole bunch of example characters which are (very poorly) disguised well known heroes, so if the player wants to "be Superman" he'll have a ready made character in the book.
This means it's a setting everyone knows well, too. You can play it in your own city, which makes it easy for the DM. While in normal games questions like "Is there a big library in this city?" require lots of making stuff up, now both players and DM will have a pretty clear idea of what is and is not available.
(The first time I played, I was in college and new to the city and actually learned about a few new buildings that I wasn't aware the city had. But it also saved me from having to make up any new locations, and poor descriptions don't matter when everyone in the group has been inside the building a scene takes place in. It lowers the bar by a lot for the DM.)
For the DM
This game has very low book-keeping, which makes it easy to run for DMs. Making monsters is easy as they just follow the rules for players, there's very little bookkeeping (the game doesn't use hitpoints and most powers have unlimited uses or very real roleplaying limitations to their use). It comes with an example adventure, you can use any of the listed player characters as villains and there's a chapter on using normals in the game.
Plus, because you're using regular people half the time things don't even need stats. You can just assume that the hero can beat up the mook unless there's like a dozen of them, and they're armed.
In my experience, if the DM can come up with a fun story (or sometimes even a fun starting point for a story) the rest will follow naturally, with very little need for heavy prep work or needing huge amounts of mechanical things.
The last game I ran had little more prep than "The characters will be inside a maglev train, which is also carrying something valuable in a safe, and some guys will try to steal that thing." From there on out, I decided one of the villains would have laserbeam powerz to cut open the safe. I made a grand total of 4 characters to fill out the team of bad guys.
With these 4 character sheets, I ran a game session spanning a full day. The story went completely different from my expectations when the players startled laserbeam-guy while he was cutting the safe and he swung his arms around, accidentally cutting the train in half and stranding it in the middle of an uninhabited area... but it worked out really well. Due to the superpowered nature of the game, most of the things that require lots of little rules in a grittier or more realistic game can be easily hand-waved here.
Also, the game lets you throw together new mechanical creatures very easily. One of my games required there to be a Troll for the players to fight in the middle of the game. Making one really was no more complicated than "Hmm, it should be big and strong, have claws, and regenerate damage" and then quickly assigning it some appropriate ranks in the Size, Strike, Super-Strength and Regeneration powers. You can set these up in 5 minutes and use them for a scene, and if they survive and have to return later you can always flesh them out more afterwards. Since there's no spell selection, complicated balance rules or attributes that affect dozens of things in the creature, there's little chance of accidentally ruining something.
For the players
One of the main things I dislike about certain systems is the first time you introduce new players and they ask if they can play X is that you must tell them "no, because that's too powerful/difficult/I don't know how". Mutants&Masterminds allows EVERYTHING from the start, with reasonable balance still in the game. All the powers scale exponentially, but you can pick whatever you want. Even things like manipulating time itself are available (albeit with a "please ask your DM because this can ruin stories" notice).
Here's some of the characters I've seen played, to give you an idea of the kind of things that are possible. Most of these were played (and played well) by first-time players:
- A modern blind samurai
- A guy who could turn into a lightning storm and teleport through eletricity-masts
- A shapeshifting druid who would turn into crazy beasts
- An inventor who would build crazy weapons in the middle of a fight
- A juggernaut who could not be moved except if he wanted to
- A dwarf who controlled the earth and made earthquakes and the like
- A regular guy who was so lucky he could operate inside a super team (he had no real superpowers, just the ability to change die rolls to a 20)
All of these were quite balanced, some were crazy superheroes, some were regular people. Due to the powerpoint mechanic, all of them could work very well together.
None of these had any complicated mechanics; most characters only have about 5 active powers to worry about. Even some of my players who were turned off by the complexity of games like Dungeons&Dragons had no problem running these.
Another big problem with running a game as a new DM is dealing with players who come up with difficult plans. M&M has a built in mechanic for when players do something that the DM does not know how to deal with (ie; plans that would circumvent the entire rest of the story) in that he can throw up a complication or even just say "we can't do that because it would break things" and award the players with special storypoints that they can later use to do cool stuff, to take away the sting.
This allows a bit of railroading around really complicated or storybreaking things without the players feeling bitter about it. The points can also be awarded for when players do really cool things, to reward coming up with over the top things.
As an example, during one of my first games as a player, the storyteller had two villains in a scene. One active threat and one merely observing undetected. Unfortunately for him, I had a character who had radar-vision and superpowered-tracking skills; and I would have no problems detecting and following the second, more powerful villain.
Upon stating I wanted to follow the sneaky guy while the rest of the team took off after the main trouble maker, he realised that I would either be able to circumvent half the story (by easily tracking what should be a hidden villain) or get myself captured/killed (by confronting someone we wouldn't be able to deal with even as a complete team)
Instead, he told me the enemy villain fled down a drain and managed to "somehow evade me in the sewers". In most games this would be a real let-down, but because you get a special token which is only awarded for being awesome (normally by doing amazing in-character things, but also when you outwit the storyteller) it doesn't feel like that. It just makes you feel cool and lets you jump back into the rest of the story. It's a combination of mechanics, setting and consensus around the table that you're running a superhero game that makes it work.
Level progression is simply spending more points, just like character creation. This means no picking classes or having to match certain things together; you just upgrade whatever powers you found coolest or select new ones as you will. Plus, you get points at every session so you CAN upgrade something at every session, or wait a bit to get enough points for something really cool.
The game's scope runs from ordinary People (Power Level 1-3 or so) to creatures that make even Superman poop his pants (at the max Power Level 20 you can do just about anything you want)
The crazy weapon builder I mentioned above for example, was originally supposed to play like a guy who carried around a bag of infinite weapons. But when the story began, the player realised it was more fun if he'd make them himself. From then on out, over the course of 2 or 3 sessions, he invested all his points into powers that would let him build new things in the middle of a fight. The switch from weapons-guy to crazy inventor came very naturally that way, and let him completely re-envision his character. That's something not a lot of systems seem to allow.
The game uses only one type of dice (of the 20-sided variety) and all of this goodness comes in a single book. You can optionally buy a settings book for more information, samples, etc, but I've never used any.
Plus, you can get the open rules for the game for free here: http://www.d20herosrd.com/