Well, I would
love to see a modern BTTF game (heck, I would
love to work on it) but it would be the decision of the rights holders (Universal I think) to decide to make a game. For example, the license would come up due to Universal deciding to re-release the films theatrically and wanting to make a cash-in game, and then various game studios would pitch for the work.
Creating a game on current console hardware, such as the 360 and PS3, is
very expensive and time consuming. You are probably looking at around two years of development time, and involve around 50 -80 staff in the studio, plus around 200-300 extra people on the external producers, management, marketing, translation, legal and testing side of things. So thats about 15 -18 million dollars for the studio time alone, then you have the cost of the external team and marketing to add to that (another 5-6 million easily) It all adds up considerably.
I guess that Ghostbusters is a much easier sell to the marketing people and bean-counters to justify the cost of making a game, simply due to the fact that its very easy to pitch Ghostbusters as a game idea. You run around and shoot things. Executives can understand that. The typical 360/PS3 gamer audience will buy that. Ghostbusters is a well known, loved and visible brand which is easy to understand and market. Everyone gets the idea.
A BTTF game will be much harder to sell unless there is a major tie-in event to push the game, simply because the story and theme behind the film is quite involved and trying to translate that into a game would be very difficult. Trying to get the average player to think about multiple timelines and cause and effect could be hard! A lot of games on modern consoles fall in into "safe" genres, such as first person shooters, racing games and RPGs, because they will sell, regardless of how good the game is. BTTF doesn't really neatly fit into any of those genres.
I think some sort of 3rd person free-roaming adventure game would be the best bet for a BTTF title. Probably playing as Marty, there could be an area of Hill Valley for you to explore in each of the time periods, and you would be recreating events from the films, but also allowed to make choices which would contradict those films, so you could screw around with the timelines in new ways. And of course, you would be able to drive the DeLorean and hit 88mph
I think a lot of the gameplay would come from interacting with characters in each time period, performing tasks and using the DeLorean to be in the right place at the right time for an event to occur.
Film/game tie-ins are very common, so you never know it could happen. If Universal did decide to re-release the films theatrically then I think there would be a good chance of a BTTF game. I cannot guarrantee what it would be like to play though!
