I've seen a lot of these discussions and from what I can tell people who like FO3 most usually have either of these arguments shaping their opinion:
1. It was the first Fallout game they played, so it feels more natural to them than FNV.
2. They just like the setting more (and haven't tried the FNV expansions).
3. They are casual gamers, non-rpg gamers or just don't like to read a lot of dialogue and interact with NPCs besides killing stuff.
4. It had been too long since they played FO3 when they tried FNV, and couldn't compare them fairly.
Most people seem to fall into the first and second categories.
You played it for years, and call it a dissapointment? I do not quite follow honestly....
EDIT: goddammit DP'ed again, sorry guys, shift sleep schedule switching is a tedium, please try to understand.
Ha ha, I fully understand. And yes, it can be better than nothing when you've just played FO1 and 2 too many times and still be disappointing in comparison.