star wars : kotor 1 & 2 : amazing games but getting abit outdated, youll want to grab alot of mods to bring it up to date graphically,
force unleashed 1 & 2 are great , rpg element is abit light but its a themepark ( you do lvl to level, not open world )
Marvel ultimate alliance 1 & 2 are great if u enjoy your comic book kicks,
then there's fallout 3 ( i wouldn't recommend new vegas, but might be ur cup of tea ) which has a great story arc & awesome rpg elements, modding community is huge.
just wanted to recommend something different to the normal fantasy rpgs listed above