[Fallout, I like the setting. I've played Fallout 3 but the AI is really dump there, is it better in 1/2?
Fallout 1&2 are almost completely different from FO3&NV in everything except setting. You would have to look up a LP or something to see everything.
Even in story they are completely different, at least fallout 3 is. Fallout 3s story was focused on cheap laughs. There wasn't much focus on seriousness, bar 1 quest, Andale I believe it was called, was the only one that matched the previous tone.
The combat is completely different, it's a shitty turn-based in the originals(which is less noticeable to a novice, basically the reasons it's bad is something I don't try to explain because it only becomes bad when you compare it to something that did TB better, IE Jagged Alliance or X-Com.), and a shitty FPS(Floaty walking, low power weapons that sound like pop guns, lack of a noticable impact when you shoot guns, over reliance on shock factor gore, doom level AI(run forward and shoot), poor quality animations, illogical enemy placement, Illogical amounts of HP bloat, inaccurate frustrating weapons, and I could go on.) in Fallout 3 and NV.
As far as deep RPGs go, Fallout 1/2, Arcanum: Of steamworks and magicks obscura, and Planescape Torment are the standard recommendations. For more modern action based affairs, VtM:B, is about as close to a modern FPSRPG with deep story and strong emphasis on systems. Unfortunately it descends into a boss rush towards the end as Troika ran out of money and time. Being forced to release 5 months early and compete with Half Life 2 on it's release date.
Of those the ones I really recommend are Fallout 1/2 and Planescape, be aware though, they do have a tendency to just sit you in a location and have you sort the stuff out. To some this is a strong suit to others, well it ends up frustrating them until they eventually quit because they can't figure out what the good/best solution is. It goes beyond what you saw in FO:NV, the new reno quest line has something like 14 different endings, and is a 7 faction conflict.
As far as deep Turn Based Tactics games that are light on the story, Jagged Alliance 2, and Knights of the Chalice have incredibly interesting systems, with Knights of the Chalice being the best implementation of the DnD 3.5 edition OGL content I've seen thus far.