1. Halo 2
2. Final Fantasy X
3. Ratchet and Clank
4. Grand Theft Auto
5. Call of Duty

1.Team fortress 2
2.Warhawk
3.Civ 4
4. Rome total war
5.League of legends

I really do not know, I am pretty sure I am forgetting tons of games but as small sample I can give.
1) Final Fantasy VIII
2) Final Fantasy X
3) World of Warcraft
4) Age of Mythology
5) Grand theft auto san andreas

1. Tales of Symphonia
2. Xenogears
3. Xenoblade
4. Zelda: Skyward Sword
5. Zelda: Ocarina of Time

And for kicks, ill do 10

6. Breath of Fire 3
7. Earthbound
8. Chrono Cross
9. The World Ends With You
10. Metroid Prime

Without a ranking system here are 5 Top Games for me:

Final Fantasy X
Final Fantasy XIII
Kingdom Hearts
Kingdom Hearts II
Assassin's Creed II

Aaaah! I could sense you hadn't hit your 20's yet ;)

I've 'favorited' the games in my collection here on this site in order, so there's basically a top 40 right there. These are my top 5 games, which is unlikely to ever change. I hold every one of these games in extremely high regard, to me they are as close to perfection in gaming as possible.

#1: The Legend of Zelda: Ocarina of Time (1998, N64)

#2: Star Wars Knights of the Old Republic (2003, PC)

#3: Super Mario 64 (1996, N64)

#4: Super Mario World 2: Yoshi's Island (1995, SNES)

#5: The Legend of Zelda: Link's Awakening (1993, 1998, GB)

Yes, I think Yoshi's Island is vastly superior to Super Mario World in my eyes. I've never understood what's the big deal about that game, Yoshi's Island is underrated. Outside the top 5 is where it gets a little more varied. The top 10 are all excellent games, but it is probably possible for a new game to enter the top 10. Because I live in the PAL region, I sadly missed out on certain time tested classics like Chrono Trigger.

#6: SimCity 4 (2003, PC)

#7: GoldenEye 007 (1997, N64)

#8: Mario Kart 64 (1996, N64)

#9: Super Mario Bros. 3 (1990, NES)

#10: Rollercoaster Tycoon 2 (2003, PC)

As you see, my top 10 is Nintendominant. The rest of my favorite games list becomes a little more multiplatform, but my first non-Nintendo game (besides PC) is not until #12, Soul Calibur on Dreamcast, and Medievil on PS1 at #14.

1. Legend of Zelda - Majora's Mask
2. Legend of Zelda - Ocarina of Time
3. Pokemon - gold version
4. Super Mario Galaxy
5. The Elder Scrolls V - Skyrim

1: Zelda OoT (N64)
2: Xenogears (PS1)
3: FF VI (Snes)
4: Super Mario 64 (N64)
5: Zelda aLttP (Snes)

1. Mass Effect 2
2. Fallout New Vegas
3. Simpsons hit and Run
4. GTA Vice City
5. Rise of Nations