This is going to require some estimates as some of these were 20+ years ago....
1. UT99, easily 4000+ hours, played this game 8+ hours a day for years, literally work, home and play UT99, sleep, repeat.
2. L4D/L4D2 between the two of them 2200 hours.
3. GW2, would estimate 1000-1200 hours.
4. Phantasie 1/2/3 for C64 easily spent 500-700 hours on them when i was a teenager.
5. MWO easily 500 hours during beta before they screwed it up and i quit when they launched without community warefare in the game as promised/advertised all during beta that it would be in by launch.