Zomb's Lair

I think that in a number of ways Bethesda's Terminator games are as much a precursor to Fallout 3 as their Elder Scrolls games and the Fallout series itself. They're not RPGs, but the levels are quite large and open and you can go in and out of buildings as you're exploring (and exploration is a very large part of the experience) - this doesn't sound like a lot, but it was actually fairly unusual for first person shooters of the time - many were considerably more narrow when it came to level design.

 

Future Shock was also one of the first examples of true texture-mapped 3D environments and mouselook control - Quake didn't come out until the following year. The controls feel great even now, which is something that can't always be said of games of this era (other than simple point-and-click affairs).

 

It's really atmospheric, with dark, demolished cityscapes to explore as you try to avoid (or confront) various robotic enemies. The sequel, Skynet, is also quite good and much in the same vein, but they've replaced the sprite-work in briefing segments with some extremely schlocky FMV sequences which are hilariously entertaining, but not necessarily an improvement.

 

Bethesda also made Terminator: 2029 and Terminator: Rampage prior to these but, honestly, neither of those are very good (I think Rampage is especially poor) and, in my opinion, aren't worth your time. These two still hold up well even today though.