Would use it to make 50 $10 million games in a wide variety of genres. Why make one game better than Destiny when you could have several?

I would start action adventure franchise called Legend of daZel, in which drag queen daZel is kidnapped by evil Cannoncock.

Pink, young futanari, needs to rescue her by fighting and solving puzzles in numerous sex dungeons, all the while searching for only thing that can defeat evil - Master Dildo.

Games would be made in photo-realistic fashion, they would be Android exclusives and would include insane amount of 'cosmetic items' In-App purchases.

Franchise would be heavily advertised during all the major sports events.

I'd split it into ten 50M $ games

a mmorpg pokemon game.... the i dunno what will i do with the 450 million though

I would try to make a game that merges two popular genres, endless game and match 3 puzzle...wait, no I meant MMO and FPS.
100 million to develop the game
50 million set aside to develop DLC
100 million for initial marketing cost
100 million for future marketing cost
100 million to setup and run servers for several years
50 million leftover cash to cover "miscellaneous" expenditure
Total = $500 million game

I'd finish Agent, The Last Guardian and Half Life 3 :')

But for real, I'd make The Last of Us combined with DayZ and free-to-play. A map which is just one big city, about the size of GTA 5's whole map. 32 or even 65 players each servers with The Last of Us based crafting and scavenging. The game would feature a huge character creator so everyone can make their unique character and everyone would start of with just one set of clothes. Throughout the game, you can find thousands of different customization items such as hats, masks, shirts, pants, shoes and different sized backpacks to customize your character, and if you're lucky you could find a bullet proof vest so you can only die from headshots and getting shot in your arms or legs, but obviously it would wear out over time. Infected would be everywhere, like everywhere. The game would also feature attachments you can find to increase damage over range, accuracy or a larger clip. The game would also feature making your character better in skills such as crafting speeds, reloading speed, running speed, running distance, the ability to shiv Infected while they are on you, listen mode distance and listen mode time, which can only be used to locate infected and not other players. Also, melee upgrading would return. If a player dies, he/she loses all their weapons and respawns with nothing but a pistol with 1 clip. He/she however keeps their clothes they found. The game would also feature a trading system. Maybe you have an extra gun while another guy has a molotov, wanna trade them? Sure! The game would be monitized in one simple way: extra customization items and nothing else.

The leveling process would produce Lots of Beautiful nekkid women running around everywhere I'm the game and cocaine would be the in game currency -  Instand hit 

i would do a deal with Victoria s Secret to use model likeness s and lingerie DLC packs (free to the gamer). 

I would get two or three brillant coders, and we'd spend a fraction of the money making the greatest, most inovative small budget game since the original NES days. Then, I'd give back the rest of the money and die happy.

i'd make 10-20 AAA vita games :D

I would give 50 talented young teams (i can trust not random strangers) 10m each.

Would probably result in 50 better games than a regular mainstream game.

I would also not expect to make any money with the games I just want my 500m back. And if they would generate more than 500m I would invest all the profits in making the games better for free.