Pretty easy:

Halo reach

NHL 11

Madden 11

Forza 3

FIFA 11

1: starcraft: Broodwar

2: Starcraft 2

3: Warcraft 3

4: Age of Empires 2

5: Pokemon Yellow

1. Wolfenstein: Enemy Territory (PC)
2. Civilization IV (PC )(or V, depending on how I end up liking it, especially after all expansions, mods, and DLC)
3. Final Fantasy X (PS2)
4. Metal Gear Solid 2: Substance (PS2)

As for the last one, I don't know. Another Civ? Baldur's Gate? Titan Quest? Obviously it ought to either have very good replayability or be one of the finest games ever (like FFX and MGS2). FFVI, even though I've managed to miss it so far?

1. Aion

2. Lineage II

3. Guild Wars II

4. Call of Duty 4

5. Halo Reach

I would take:

SimCity 4

Alpha Centauri

Smash Bros. Brawl

Disgaea 2

Galactic Civilizations

Basically, games that I can play over and over and over again for...ever.

Hmmm... only 5...:

5. Gran Turismo 5 (OK, not released yet, but would have loads of playtime)

4. Super Mario World

3. An Age of Empires game, not sure which one as I pretty much loved them all.

2. Oblivion (with mods)

1. Deus Ex

honourable mentions: Starcraft, KoToR, Dragon Age, Mass Effect 2, GTA: San Andreas

Tetris

Super Mario Bros 3

Donkey Kong Country

The Legend of Zelda

FF6

1. Final Fantasy IX 
2. Super Street Fighter 4
3. Team Fortress 2
4. New Super Mario Bros. Wii
5. Yu-Gi-Oh! World Championship 20XX (*whichever has the most cards and plays the actual card game format)

almost like me !!

Super Mario World

Super Mario Kart

Wind Waker

Red Dead Redemption

F1 2010