id make a classic rpg, it'd be 3D but a tactical view of cartoonish sprites, you could customize UP THE BUTTHOLE with different armors (as in shoulders/gauntlets/breastplate/leggings/shoes/helmet/accessories) and your customization for skills would also be ridiculously in depth.
it'd be party based, but in the case that if you have a friend over, your friend could tag on and use your party member (they would be defined to one while you control the others) so you could have up to a 4 player co op going on in the rpg.
of course being as i love stories, it would be heavily story based, however there would be tons of side quests based off each character that would actually make a difference later on in the end game (such as who pops up where and if they aren't dead already)
hopefully with the tactical cartoonish sprite graphics wouldn't take up too much of that money so all the rest could go into customization and story development.
and of course this would be sold on all platforms, ftw for everyone!