http://en.wikipedia.org/wiki/Fallout_(video_game)
http://en.wikipedia.org/wiki/Fallout_2
http://en.wikipedia.org/wiki/Fallout_Tactics
http://en.wikipedia.org/wiki/Fallout_(series)
You should expect them to be absolutely nothing like Fallout 3 whatsoever. Which for me at least, is a good thing. You'll be able to appreciate a balanced and working SPECIAL, trait, skill, and perk system. The games don't break any visual boundaries, but their strength has always been in gameplay and story.
Fallout Tactics has undergone an artistic overhaul, and looks better than FO1 & 2, but has almost zero RPG elements whatsoever. It's a solid combat-centric game, with an interesting spin on the combat system of the originals. It doesn't try to be something it isn't, it boasts a strategic and combat-centric experience, and that's what you get.
My personal favourite is FO2. Though I'd suggest you play FO1 first, as the stories are linked, and FO2 has a few more engine/interface improvements. If you play FO2 and work your way back, I feel it might spoil your FO1 experience.
You should check out this http://www.gamesas.com/bgsforums/index.php?showtopic=681908 and scroll down to where
Geronimo57 has posted up some very handy links to patches, mods, and manuals, all are recommended for their quality and safety. You should also check out the rest of the thread whilst you're there.