Counter-Strike

THE GOOD:
- simple, yet addictive
- countless number of strategies
- scrimming with 4 other friends

THE BAD:
-limitations of the HL1 engine
-the multiplayer scene is often viewed as pretty immature (just read some of the gotfrag forums)

SUMMARY:
This is the true definition of gameplay over flashy graphics. Many awesome looking games have come out over the years, but CS has outlasted all of them and it came out in 1999(i think). Even with its simple looking graphics compared to today's standards, this is one of the best online shooters ever. If you want, you can even join leagues with your clan such as CAL or UGS. Scrims are incredibly enjoyable and will keep you playing for a good while.