I've played through and completed 3 RPGs so far for the 360.  Fable II, Infinite Undiscovery and Tales of Vesperia.  Out of those 3 ToV is by far my favorite, but I really feel that each game holds it's own.  I only played through ToV to beat it and it took 60 hours.  There is still so much I have yet to do in the game.  Currently though I'm playing Enchanted Arms.  I'm actually amazed at myself because each game I have played to the full I started and didn't stop till I finished.  I'm also on disc 3 of Lost Odyssey, but I haven't got back to that one in a while.  I might finish it after the current game I'm playing.

So what about you guys, what is your fav 360 game?

 Thus far my favorite 360 games have been Halo 3 and GTA IV.
 I have Fable 2 and have enjoyed what I've played of it so far, however I am only just now at the part where you become an adult.
 I also have Mass Effect and am very much looking forward to playing it. I want to finish the other games first though.

I would urge you to go ahead and give it a shot. From what I've come to understand Mass Effect plays primarily in third-person but controls similarly to a first-person game (somewhat like RE4). I believe that there are first-person controls for certain circumstances such as aiming a sniper rifle.
 I wanted to play Mass Effect largely because Knights of the Old Republic is by far my favorite RPG. Even without the Star Wars connection it is an amazing game. I never got a chance to play Jade Empire, but since Bioware did such an amazing job on KOTOR I figure that Mass Effect will be awesome as well.

Mass Effect is completely in Third person view, just like the rest of Biowares games.

During battle,you press the shoulder button and the camera zooms in slightly over the shoulder and the aiming reticle comes up,still in third person. You can get a new copy for 20$ and I highly recommend it.

Resident Evil 5. I totally didn't die 3 times in the first five minutes. <___<