Getting mod to work with this game is the biggest pain ever, even worst than Skyrim. I'm so jealous of those that know what they are doing.
I really didn't - I just went through Gopher's excellent Youtube series (invalidating my own long held theory that there is no wisdom to be found on Youtube) and followed along. Before that, I added some mods strictly for stability and to kill the stutter and micro-stutter; they went smoothly even though it was my first time modding ever. It was only after my second play-through that I wanted to add content mods and thus had to learn how to find conflicts and make blended patches, which makes the process a lot less hit or miss. Also, another ATer (thanks again, Allen!) sent me a written summation of each step in Gopher's series, which made following along MUCH easier and quicker.
There is a new mod manager, Mod Organizer, that is supposed to greatly improve ease of modding and conflict resolution by leaving your base game unmodified and building a unique database for each configuration, with conflicts resolved on the fly. I was going to replay New Vegas with that, but given the Institute content decided to replay 3 instead, with my current mod list, so I haven't yet tried it, but a lot of heavy modding talent are behind it.
Counter-Strike. I've been playing it for nearly 16 years now, and I still play it regularly. Unlike poofy, I hate GO; if everyone stops playing Source, I may well stop playing CS for good.
Beyond that, I can't think of too many games that I keep coming back to years down the road. I always load up Crysis and Crysis Warhead when I upgrade my machine, just to see how they run now; given that my 980ti will be arriving next week, looks like I'll be doing that again in short order. I'll probably end up playing thought both campaigns too, because why not?
What specifically do you dislike about GO? Like Poofy, I found it to be all win, except losing a lot of my community-made maps.
I really enjoyed FC2 as well, although not as much as FC3. While, some of the mechanics are negative (no fast travel, respawning enemies) I don't really understand the hate it receives.
The only things I disliked really were the insta-respawns which break immersion and the silly ending. FC3 was far too cartoony and consolish for my tastes.