I have the original, Fallout 2 and Tactics as part of a free promotion Good Old Games did a while back, but I've not put any significant time into any of them in all honesty.

Fallout 3 is one of the best games of the last console generation in my opinion and I think I made the mistake of renting New Vegas too soon after completing 3, I was burned out on the mechanics at the time and never really gave it a chance. When it goes on sale again I'll give it another go for sure.