The old Fallouts aren't for everybody. In the same way that not everyone who enjoyed the original games liked Fallout 3 - if you liked Fallout 3 it's by no means a guarantee that you're going to have much fun with the earlier ones. There's certainly a lot of people who like both, of course.
If you're looking for an experience that's akin to Fallout 3, you won't find that in Fallout 1 and 2. If you like isometric turn-based roleplaying games with a bit more of a learning curve (I never had trouble with it, myself, but everyone's experience will be different - it does have extensive in-game documentation,) then you'll probably like Fallout 1 and 2. If that's not your idea of a fun game, then honestly you probably are better off without it (because that's what it is, obviously.)
Also, none of the events in Fallout 3 are really connected to the older games, either. This was done on purpose, of course - they wanted to reach a wider audience this time around without having to retread ground covered in previous games. If you're interested in just seeing more of the background of the game, then it might be useful. But playing the older games I don't think is really going to illuminate Fallout 3 to any great extent, either. You'll get some of the "in jokes," and Easter Eggs, but I wouldn't expect too much more, to be honest.
It's kind of hard for someone else to you if you should buy a game or not, though. I mean, I can't tell ahead of time what you're going to like. For example, if you
really want to start at the beginning, you have to go all the way back to the franchises spiritual predecessor, Wasteland. (Which was what, for the Commodore 64 or something like that, originally?) The game was so old-school, you had to play the game with a little choose-you-own-adventure sort of book... I like my classic games, but I have to admit that was a little over my own threshold.