First off is
Tremulous
This game is fantastic
Graphics- Quake 3 level GFX
Gameplay- Unique RTS/FPS Hybrid
Plot- None really Aliens vs. humans
Bad things- Gets boring after about 5 hours of gameplay for me
Second is
OpenArena
This game is pure multiplayer FPS
Graphics- Decent Quake 3 like GFX
Gameplay- Pure run and gun FPS
Plot- Absolutely None
Bad Things- I got nothing
Third is
Shoot Em'
Pure ASCII
Graphics- 3D ASCII!
Gameplay- It's pretty much a minigame but has online highscore tables
Plot- ASCII in 3D what can I say does it need a plot?
Bad Things- You are stationary and can only look around
Forth Fifth and Sixth is
The Marathon
For true and untrue Halo fans alike
Gameplay- Old School FPS action, Doom like, Online play included
Plot- This trilogy is the follow up to the Halo Series though it was made prior to
Bad Things- none, additionally it runs on PC, Mac and Linux
Seventh is
Gunbound
Gameplay- Strategy
Plot- No Clue
Bad Things-No Clue I have never played it
Eighth is
America's Army
Gameplay- "Realistic" FPS
Plot- It was made as a recruitment tool for gamers to join the army
Bad Things- My comp runs it very crappily
Ninth is
Gunz
Gameplay- 3PS
Plot- Shoot people
Bad Things- I installed it but could not get it to run
Tenth is
Rakion
Gameplay- MMORPG
Plot- No Clue
Bad Things- I dunno my friends like playing it
11th is
12 Sky
Gameplay- MMORPG
Plot- Three warring factions are at war
Bad Things- I participated in the Closed Beta so I suppose that the gameplay might of changed, but leveling was tedious and took forever and a day
12th is
War Rock
Gameplay- FPS with some RPG elements
Plot- War
Bad Things- No Clue
13th is
Maple Story
Gameplay- If SMB and WoW had a babt this is it
Plot- I dont think there is one
Bad Things- After it updated I wasnt able to log in as often, I will play this game again when I get a new comp
14th is
Passage
Gameplay- You walk around, it is very artistic
Plot- Your trip through life
Bad Things- none this is a cool short game
15th is
Sumotori Dreams
Gameplay- Funny Physics Game
Plot- None
Bad things- There isn't more games like this
16th is
fl0w
Play the game before it got ported to PS3
Gameplay- Arcade like
Plot- Micro organism stuff
Bad Things-none
17th is
Alex The Alligator 4
A must play platformer
Gameplay-Platformer
Plot- Save Your Woman from becoming a pair of boots
Bad Things- None
Because I have no racing games yet 18th is
GeneRally
Fun Racing Action
Gameplay- Racing
Plot- Race
Bad Things- The graphics are almost too minimal
Ninja 19th is
N
Crazy awesome and simple
Gameplay- Platformer
Plot- I dunno
Bad things- None, it's even heading to XBLA as N+
20th is
Super Mario War
Amazing Retro Multiplayer Action
Gameplay-Multiplayer Fighting Platformer
Plot- Kill your Mario Bros.
Bad Things- also has a DS port and that makes me jealous
21 is
Charles Barkley's Shut Up and Jam Gaiden
RPG+Basketball+Randomness
Gameplay: Final Fantasyish
Plot: Absolutely crazy amazing
Bad Things: RPG maker can often have bugs
22nd is
EOU
8-Bit MMORPG
Gameplay: Nethack, Ultima, and Diablo based
Plot: make a 8-Bit MMORPG
Bad Things: I got bored, mainly because not many people play it
Good Things: Small installation, Works on Many PCs, Free
I will update this later on of course