Yeah, there's way more quests in NV than in F3. Definitely more marked quests, though not sure about unmarked ones. I think there might be more quests than Oblivion, too - it certainly feels that way. The tradeoff is that there are much fewer random dungeons with no quest or logic attached to them (which were bloody everywhere in F3 and Oblivion), though in my personal opinion that's not a tradeoff at all but a welcome feature.
oblivion had about the same, if not a few more quests than F:NV. i dont know what bethhedia was thinking releaseign a game with 14 quests not attached to the main quest(speaking of f:3)... i mean really?
edit. just checked fallout 3 vault wiki. 17 quests. i was close. thats still not enough.