Ok here are mine, from most favorite to least favorite, but they all are great.
1. Quake 1 (got me into map creation, and the best multiplayer ever - used to play it in middle school with everyone i knew and didn't know)
2. Doom (Doom is a classic that can't be beat, nor replaced)
3. Daggerfall (most complex and largest scale RPG to date. World is procedural but who cares, the damn game is so well done - and besides, oblivion is just as repetitive)
4. HeXen II (Mashup of RPG/FPS hybrid, this game is incredibly difficult but rewarding to play, there are many well created puzzles, and coop support make the game extreme fun)
5. Final Fantasy VII (need i explain this one?
)
6. Thief TDP (Great stealth game, leagues ahead of most stealth games including MGS)
7. Metal Gear Solid 1 (great game with an amazing storyline and fun gameplay. The well developed characters and twisting plot put this game through the roof)
8. Descent ( first 6 DoF game, along with many games of the time had kick ass gameplay and music [such as this song
http://www.youtube.com/watch?v=XZT4mJxv4zU], and multiplayer was a blast - the freedom of movement created a whole new type of deathmatch)
9. Unreal -
NOT unreal tournament, the single player FPS that started the series (This game i love like a lot of others, but this game makes it here for Its memorable presentation and design. The graphics were amazing for the time, and the world was truly breathtaking. Unfortunately, you rarely see the types of environments this game had in an FPS anymore. It remains one of the most creative FPS games ever made. Want proof? just look at Nyleve's falls or the Sky town - and the music in this game complemented the environments perfectly - it seems a lot of old games did a better job at this than most newer ones)
10. Crysis (People say graphics aren't everything, and this game is proof of that. Despite being the most stunning looking game ever made, so much pure detail in everything, it
still manages to be fun and introduce new gameplay concepts that keep the game from being more than just a pretty face. On top of that, the level editor is the most amazing I've ever seen for a game)
Honorable mentions include:
Half-Life:This was a close one for me, between Crysis and HL, even though HL is from my childhood - i ultimately chose Crysis because of the things that made it last longer for me, such as the open-endedness, and the ability to create amazing things with the editor, where as half-life editing was like Quake 1 (same engine) but i enjoy Q1 editing much more. Also, it didn't make my list because I feel this game somewhat attributed to the death of the truly unique shooter. It was a hallmark in game design, but the design of the game, just made more sense than games before it. Quake and Unreal had more unique environments, but while Unreal made more sense than quake, they were both still unique in their own ways and were more based on fun. And the weaponry in HL, is, well...normal. You see many similar arsenals in other games now. Even futuristic games don't have unique weapons anymore like Unreal or Quake 1 do.
Duke Nukem 3D: Despite being a major part of my childhood gaming experience (albeit with parental lock on) this ultimately had to miss the list. What it did do right was bring environmental interaction to a new level in games. But it does feel a bit immature playing it now. I still feel its great, but not for my top ten. Not anymore at least. Sorry Duke.
Battlefield 2: This lost out to the classics, but if there was a top 11, this would be in it. This is
the best MP tactical game out there, period. Never has a blend of vehicles, infantry, squad tactics, and semi-realistic gunplay been so well implemented. Screw you, Bad Company 2.
Far Cry: Yes, it is better than Crysis, but i still had so much fun with both, I picked Crysis for being more well polished and because i use the editor for Crysis more.