For myself it started with Jedi Knight, and then eventually mods on the Source engine (CS:S / HL2). To me it’s a good way to get people excited about the possibilities of programming at a fairly young age.
And same. Me personally, I learned Java to mod Minecraft. That's how I got into programming. Overall, I'd say modding is still in pretty good shape.
(And yes, I've played TR quite a bit!)