I have to admit to Oblivion being my first "RPG" experience...and I really enjoyed it, unbelievably I let Fallout, Baldur's Gate and PST all pass me by when they were released, I was busy playing Half Life and Quake 2 in college, System Shock 2 came along and I started to realise that there might be more to less linear games but I watched Morrowind pass me by too, mostly because my PC had no chance of running it at the time.
So basically up until the last few years I've been an RPG virgin, Fallout 3 was my second RPG and again, I really enjoyed it but the sheen wore off quicker, I went and played Fallout 1&2 afterwards and got a taste of really high quality writing...talking to some of the lobotomised cliches who bibble their way around the capitol wasteland was never quite the same afterwards.
Now saying that I went back and completed Fallout 3 another two times, there's still enough stuff I haven't seen to make one more run worthwhile, and I'll do it because I really enjoy the exploration aspect, plumbing the depths of a bombed out building to find skeletal remains in amusing positions or computers with depressing diaries for whatever reason does it for me.
So anyway, I do have to thank Bethesda for introducing me to the RPG, their writing sucks but Fallout 3 can still kick ass at times, also, mods are essential