Everyone talking about how you "just wouldn't spend that much on the game," you're missing the entire point of the thread.
I would probably make some RPG adventure game. I'd spend a lot of time making it really fun and polished yet not super graphically amazing or anything, then spend the rest of the money on making it the hugest game ever. Make it so huge that it takes a ridiculous amount of time to see everything. Any hole in the ground can lead to a mile-long system of tunnels. Any random NPC if interacted with in the right way could lead you on a crazy epic quest that you couldn't have seen coming, which leads to even more quests and secret areas. Just a ton of content everywhere you turn.
A game that's so big with so much to explore it actually feels like an adventure, with just so much content it can't really get spoiled or easily compiled into a strategy guide. Where even as adults we're constantly surprised by what we're finding and sharing our experiences with each other like we did when we were kids.
THAT'S what I would make if I had stupid amounts of money. These days it seems like graphics are always a big priority that suck up all the resources. Then more modest games just don't have the budget to develop that much content Give me a graphically modest game with craploads of content.
Currently playing:
Bloodbath Paddy Wagon Ultra 9
