Choose 1 gateway

If a gateway opened up and you can choose a fictional world to have access to, what world will you choose?

Rules:

1. In this scenario, Marvel and DC doesn't bind all the branches of their universes to their title. You'll have to localize your choices, like choosing X-Men or Gotham.
2. You will function as the physics in the world you're in.
3. By passing quests, you can choose to have more powerful stats/abilities that exist in the world you choose. (You can return to either world anytime you want to. Time will stop in the world you left. Your aging process is filed separately. If you stayed in one world for 40 years, you'll age 40 years in that world but in the other world your age will remain the same. The rarer the ability, the more ridiculously difficult the quest will be.
4. You can only choose to have access to one fictional universe's gateway.

Dungeons & Dragons, its a fantasy setting with great variety and alot of lore and depth, should also be possible to "level" in.

Ofcourse it should be 3.5E.

Edit: on the other side of it, Starwars is probably my second choice, but a futuristic setting rather then old.

Mass Effect Universe. 
Steal some useful tech and leave.

Elder Scrolls

@Bruxae said:

Dungeons & Dragons, its a fantasy setting with great variety and alot of lore and depth, should also be possible to "level" in.

Ofcourse it should be 3.5E.

Edit: on the other side of it, Starwars is probably my second choice, but a futuristic setting rather then old.

Isn't the lore and depth in D&D created by the Game Master's imagination? If it is than you're probably the winner in the thread. It never crossed my mind to go for a Table Top Role Playing game.

@Decoy Elite said:

Mass Effect Universe. Steal some useful tech and leave.

You can't take the items from the other world to our world. You can memorize stuff from the other world, so you can probably learn how to build it. It's going to be difficult because some of the parts that are needed to build the thing only exists in the other world. You'll need to translate the knowledge and the logics in your head.