I'm searching a scientific study that evaluated different combat systems in regards to the in-game out-game ratio. Or if there is currently non a dataset that would allow to create such a study.
There are some forum discussions on various sites on the Internet, such as this one, but notice that it is a similar topic but the original asker there is asking "how many fights per session can you comfortably fit in". If you really mean to focus on the game-time to real-time ratio, that may be harder to find, since that can range from 1-second-per-turn (GURPS) or less (Phoenix Command) to 1-minute-per-turn or more, or the commonly-used "the GM determines how much time each battle took in game time, when that matters".
In general, however, no, your question isn't going to have an answer in the form you say you are looking for, because there are too many variables which vary way too much from player to player, GM to GM, situation to situation, such as: number and speed of players (which can vary a lot depending on what players decide to do in each battle), number and complexity of opponents, how well everyone knows the rules, the way the GM runs the players, whether the situation being played brings up something the players need more time to think (or look up rules) about and how often that happens, how many players are playing and whether they're allowed/required to talk to each other during play, what time scale the game's combat system uses, if any, etc etc etc.
Even if you can decide what question you really want answered, you would need to focus your question on what you really want to know, limit the parameters and units according to that, and then find players who know all the systems you want to compare (or train up the group you are interested in, on those systems), and time them, take data, etc.
Even for very similar games, in equivalent situations, with all expert players, I don't think you're going to do a lot better than "system A seems to be faster than system B in this situation with these players," where "faster" involves two different numbers: how much real-time and how much gameworld-time.