This was an idea I had earlier, partly inspired by Smash Bros.:
While her kid is at summer vacation, a mother decides to sell all of his video games, primarily made up of RPGs. Somehow or another, an ancient book that the kid happened to have happens to get mixed in the box with all the video games. When a buyer comes to buy the games for his kids, he asks if the book is included, reading a passage out of it. The mother says she's never heard of it, so she doesn't care if he takes it.
While driving to his house, the purchaser of the games suddenly gets drawn into the box itself. It seems that ancient book just happened to carry a spell that brought things to life, and by reading it, the man was drawn into this newly created, combination-of-RPG-worlds world, known as 'Box'.
Yeah I know, not a very good story, but its meant to be light hearted, so don't take it to seriously. Anyway, this game is a tactics/strategy game that features a variety of characters from popular RPGs, such as Final Fantasy, Xenosaga, Pokemon, e.t.c.
The game would feature over 100 characters, so the main point of the game isn't really to focus on who is the best character. Some of them are practically the same. However, the point is essentially to create a strategy team with your favorite characters. The game would be made so, for most series, you can have an entire team made up of characters from that series. Or you could mix and match. Either way, it would be up to the player.
It would essentially be a tactics version of SSB, except with RPG characters rather than Nintendo-only.