I think the graphics are actually good :/ I mean, most other games of the time were uglier in my opinion. Especially 3D games. And all the sprites in Fallout 1 & 2 look pretty cool.
isometrics do have their very own kind of magic to them (as well as any other kind of tile based pixel art).
must've been the most short-lived art form of all times, can't have been much more than 25 years (if you set their acual LIFEtime-span from say zaxxon to sims). pitty for me, as i happen to have been kind of a grandmaster in it...
as for getting the games or not: it's great gameplay, no more no less, and i'd say you can absolutely forget about the graphics, because after an hour or two you'll be so deeply into it you'll not even notice anything unusual about it anymore.