Jagged Alliance 2 is one of those games that you can keep coming back to, even after all these years. The graphics are pretty dated by now, but there is so much to the game that it doesn't matter.
There are enough different mercenaries to hire that you could, if you wanted, play through at least three or four times without using the same characters twice. Each merc has his/her own unique personality, voice, and abilities. One of the coolest features is that certain mercs like or dislike certain other mercs, so if you have say, two that don't like each other on the same squad, they may complain or even quit. If you have two that like each other on the same squad, and one of them dies, you may just be treated to a special eulogy by the surviving merc.
There are tons of areas to visit, and special events that you may miss on your first run through, so it's worth it to play again. About the only real complaint I have is that towards the end of the game, most of the enemies carry rocket rifles, which are much too powerful. This results in a save-and-load situation, because if someone with a rocket rifle gets the first shot on you, you're pretty much doomed.
JA2 is a great game though, and if you ever see it in a bargain bin, I recommend you snap it up without a second thought.