>>2
I thought 4X described Civilization style games? Aren't X3 and Freelancer in the space sim genre, with trading elements?
OP give us a few games you like and what genres you enjoy like RPG, FPS, RTS, TBS, etc.
I'd suggest downloading one of the Total War games, probably Rome or Medieval 2, whichever time period appeals to you more. The series is incredibly addicting, it has a TBS campaign map, so it can have most of the complexity of 4X games like Civilization (though its a lot more warfare-based than technology) but when you go into battle, it goes into real-time tactical. Similar to an RTS, but where formations and positions matter heavily, a lot more complex than the average RTS. I think Company of Heroes and Men of War are some of the better examples of RTT's (though they're usually classified as RTS').
Also, Mount & Blade: Warband is pretty fun. It's like Medieval 2: Total War, but you get to play as the general and fight in the battles, and has a much heavier role-playing element, with a lot of things fleshed out like towns , kings/lords, and just how you work your way up, since you're only playing as one person, not a whole faction. You still (eventually) take control of giant armies and can end up being king of a whole countries. Its not very polished though, graphics are ugly, glitches and bad AI, but it has that special charm to it, and is also addicting. You can also play online with the pirated copy, but the online isn't that great, feels more like a mod to Counterstrike than its own multiplayer, they matches are just team deathmatch and attack/defend, instead of having the whole world map and factions and everything thats in the singleplayer. Though there's a mod to add those in, Strategus, haven't it tried it yet.
For shooters, Metro 2033 has a fun storyline, but the combat is pretty boring and gets annoying. Unpolished like M&B, but it has some great sections, especially in the small 'towns' at the stations. They feel surprisingly real, even with the shoddy animations and horrid voice acting. The graphics are pretty great too, gets better than Crysis at points, but then again its all mostly hallways so that isn't saying TOO much.
Also, Stalker Shadow of Chernobyl, if you haven't played it, you definetly need to. FPS/RPG mix, not VERY RPG-like, just an inventory and looting, but the FPS part is very brutal. Weapons deal high damage (to you and to enemies), mutants can come out of nowhere, ammo is scarce. The game does not hold your hand, but it has one of the best atmospheres I've ever seen in a game. Can get really scary too, and not just pop out surprise scares, most of the game's 'moments' are random events because of how the A-life system works, also creates a LOT of replayability. I recommend the Complete 2009 mod on your first run-through, just improves graphics, has a few minor changes but nothing TOO big that would ruin the vanilla experience. Biggest changes are a sleeping bag to pass time quickly, very rare/expensive repair kits so you don't have to travel back to the guy each time something breaks, and they take out a few memorable lines like "get out of here stalker", so that they only say it once, instead of repeating it over and over. It also makes the save take a while to load after starting up the game.
Oh and Amnesia is a great survival/horror game, if that's your thing.