Bioware makes character driven games and the ME2 crowd was for me dull in its stereotypical portrayal, whether they be out of a blockbuster movie or out of Bioware's stock dialog and drama that they've collected over the years. That and I disliked the gung ho protagonist from the voice to the responses. That said over the years I've developed a strong antipathy towards the sci-fi blockbuster partly because I liked them too much when I was a kid and partly because my taste in movies has refined.
The game is essentially a homage to something I can barely watch now which makes me more biased then most.
FNV felt novel, like most sandbox games the first time around. Lots of stuff to explore, some of it clever and interesting. The weapon sound/visual effects of the wild west arsenal was a lot of fun for as long as it was viable. When we got to the Fallout gear, I started to lose interest. In fact my interest was directly proportional to the ratio of wild west elements to stock fallout themes, with the latter turning me off in general. The story and characters were no more than a backdrop for the exploration so far as I am concerned. I'm not going to replay it, because the novelty is gone but I was quite immersed for a while.
The most fun I've had since the Witcher, even though I'd rate FNV below it.
ME2 below that, DA below that and ME 1 on the bottom.