I'll go on video game kicks a few times a year. Sometimes I don't touch them for 4-6 months, sometimes I lose a couple days a week to them. Games are great.
I still like Age of Empires II for strategy. Galactic Civilizations II is also good, but too easy once you know how to beat it (I've yet to try III though). And Risk II is an awesome strategy game, and the games aren't too long (unlike AoE).
And of course, there is always Dwarf Fortress. Which is fantastic, once you get into it, but has quite a learning curve.
I played Warcraft 3 years ago when it first came out. It was fun. Good game. Don't remember a lot about it now though, aside from some of the units, and there being heroes, which was a nice dynamic.
I'll play Diablo 1 and 2 once every 3-5 years. 2 is way bigger and also good but never matched the atmosphere of 1. Didn't know about the HD mod!
Always liked the Elder Scrolls games. Daggerfall majorly influenced my life strategy ("life is a collection of skills, and I can upgrade them all!"). Finally played Skyrim last year for the first time and it's a great game too. I also played Fallout 1 and 2 for the first time a few years ago... dated graphics and controls took about an hour to get into, but once I was into them, man, those are good games.
Don't Escape: 4 Days in a Wasteland was a really nice point-and-click old style pixel game that came out last year. Immersive but not too long. The first 3 Don't Escape games were flash games you can play free online. All are a neat concept (as is the author's "Deep Sleep" games), and the fourth one was great. Also set in an apocalypse setting, so somewhat relevant to now.
If you want a short-ish text-based game you can play free online that is immersive but not too hard, look up "A Dark Room."
If you want a short-ish point-and-click game you can play free online that is immersive and will punish you with emotionally frustrating difficulty, look up "Gods Will Be Watching."
If you're on Mac you can download Open EMU as a one-stop app to play any roms you have for Atari, NES, SNES, Sega Genesis, N64, whatever. So much nicer than when you used to have to have a different emulator for every system.
Important tip: so long as you're only playing older games it's easy to keep video gaming under control. It's only when you're playing brand new games you get sucked into spending all your time on them for unreasonable stretches of time.
So just stick to only playing new games when you have a lot of downtime (like now). The rest of the time, play old games you've already played to death that won't wreck your schedule too much or turn you into a temporary hermit
