Ocarina of Time, although I rarely finish it its always fun to start up again.
Mario Kart (currently 8 of course)
Pokemon. The latest game for competitive, Soul Silver for story and nostalgia.

Super Meat Boy - it's my favorite game of all and I have completed it (Golden God+) six times now.

• Metroid Prime Trilogy - I love to replay these, absolutely fantastic games. They don't take long to replay either, ~10-12 hours. Good for me to sink some real time into.
• IGAvanias - I come back to these a lot too, basically for the same reason I come back to the Prime Trilogy. Well constructed and good to just blast through on a spare weekend. Lots of fun.
• Pokemon - Pokemon games are strangely cathartic to play, as these games fill my need for mindless grinding pretty well. Again, they don't take as long as other RPGs to blow through either and they're pretty easy, so that's a plus.
• The Legend of Zelda: Majora's Mask - Can't resist going through the strange world of Termina over and over again. They did a great job of making an interesting world with fascinating characters, so I'm a sucker for going through and completing all the side quests, taking on bosses, etc.

• Killer Instinct - Pretty much the same reason you gave for Street Fighter
• Pokemon - With 700 pokemon and countless strategies this game becomes extremely addictive when playing competitive. It also helps that is still very fun without multiplayer
• Gears of War - This is probably my all time favorite franchise.  With a great story and a truly skilled multiplayer there is always a reason to get better.  
• Halo - Similarly to Gears of War Halo is one of those multiplayer games that involves skills and very team oriented.  With unique weapons and good balance there is always a reason to come back

anything on my Dreamcast

Tekken.

Final Fantasy VI, Chrono Trigger, Secret of Mana

Mass Effect (the whole series)

BioShock

Too many to name, but the most prominent examples are:

- Halo series
- First two Super Smash Bros. games
- Dead Space series
- Mario Kart 64/DS/8
- Mario Party series
- The Legend of Zelda: Ocarina of Time
- Perfect Dark series
- Super Mario 3D World
- F-Zero GX
- Donkey Kong Country
- All Rare developed N64 titles


Heck, you could pretty much add all Nintendo developed N64 titles to that list as well. Best aging console by far.

Uncharted 3, Journey, and Sly Cooper series are always fun to replay any time. Of course that's most of my games since those are the ones I keep permanently are the fun single player ones that are cinematic and replayable.

Stronghold (2001), mafia city of lost heaven and mario galaxy games.