It amazes me that people enjoy Fallout 3's cliche main quest, with lame characters and illogical plotlines.
I'll requote my post from just a few before yours:
Yes, what FO:NV has going for it is the variability of how you do the quests, especially the main quest. FO3's quests are clearly more simplistic and shallow, especially the MQ. Plus, there does seem to be alot more optional ways to character build, since your skills & stats are called on more in the NV quests.
What FO3 has (which powermapler got into a bit in his first post) is more random wasteland crap.
FO:NV is very well designed, but it's very focussed around it's questing. That's Obsidian's strength.
Bethesda's strength is in the random world building - all those locations that aren't marked on the map, that don't have anything to do with a quest. LOB Enterprises. The various shops / stores / factories. The interesting stories contained in the terminals (the best writing in the game, really. Much better than the main quest.) The fact that, even after six playthroughs - four of them ignoring the MQ - there are still new things I find around any given corner.
So, yeah.... while I'm looking forward to my next NV character (different tactics, different skills, different quest resolution), I still am also looking forward to playing FO3 again. Because it's much more of an "exploration" game than FO:NV is.
tl;dr - I don't replay FO3 for the crappy, shallow MQ. (to the point that four of my six FO3 plays, I've ignored the MQ) I replay FO3 for the random unmarked stuff out in the wasteland.
FO:NV (Obsidian) does the Fancy Plot? better.
FO3 (Bethesda) does the Random World Detail? better.