I'll just say that from my point of view and that of many fans of the Fallout saga, the second installment is the best of all in terms of narrative. Currently there are many mods for Fallout 2 and there is even a multiplayer Fallout based on the Fallout 2 engine. On the other hand, Fallout Tactics although not very popular, brings the command strategy to the Fallout world, something that was really cool at the time :)
If you're up for playing Fallout 2, I'll just tell you to be prepared for a very tough battle with a guy named Horrigan.... xD
Cheers.