This is the greatest thing ever.

Can anyone identify the games?

I think the second one is final fantasy tactics and the eight one is tetris, but that's about it...

6 and 20 looks like some zelda game, the eight one is on some 'online games' site (played it a few times, but i dont remember the name), no idea about the others

The 3rd one is SSB
The 6th one is Zelda: Ocarina of Time

And several of the others [such as the 12th, for example] look like they could be damn near any game of their respective genre.

First Row
2nd: Ogre Battle: Knight of Lodis
3rd: Super Smash Brothers
5th: Zelda Ocarina of time
9th: Red Ninja ???

Second Row
2th: Some Final Fantasy game, 4th one ?
4th: Virtual Fighter ???
5th: Castlevania ???
8th-9th: Doki-Doki Majo Shinpan
10th: Another Zelda, Wind Walker ???

First Row
*1st: Izuna? (certainly a roguelike)
2nd: Ogre Battle: Knight of Lodis
3rd: Super Smash Brothers
4th:
*5th: Actraiser
*6th: Zelda Ocarina of time
*7th: Mr. Driller
8th:
*9th: Tenchu
10th:

Second Row
1st:
2nd: Some Final Fantasy game, 4th one ?
*3rd: City Connection
4th: Virtual Fighter ???
5th: Castlevania ???
6th:
7th:
8th-9th: Doki-Doki Majo Shinpan
10th: Windwaker

First Row
*1st: Mystery Dungeon: Shiren the Wanderer (or Torneko)
*4th: Sin and Punishment

#8 reminds me of strider
#10 looks like an STG of some sort

Top Row Left to Right:
1 - Furai No Shiren 3
2 - Tactics Ogre: Let Us Cling Together
3 - Super Smash Bros. Melee
4 - Sin and Punishment
5 - Act Raiser
6 - Legend of Zelda: Ocarina of Time
7 - Mr. Driller
8 - Strider 2
9 - Tenchu: Wrath of Heaven
10

Bottom Row Left to Right

1
2
3 - City Connection (Arcade)
4 - Fighting Cup (N64)
5
6 - Dancing Eyes
7 - Rolling Thunder (NES)
8,9 - (Based off Dokimajo)
10 - Legend of Zelda: The Wind Walker

Sources:

Wikipedia
Google Image Search
Hardcore Gaming 101
System16
Everyone before me ^_^

I just realized bottom left is Wonder Project J2.

I don't know which one I like the most, the Smash Brother or the Legend of Zelda ones. Must be my incredible bias though.

..... are 18 and 19 Nintendogs?

#2 on the bottom row looks like a Final Fantasy, especially Kisame's pose and size relative to the others, but the menu doesn't look like a FF game.

Bottom row #5, isn't that the SNES "Ghosts 'n' Goblins"?

2nd one on the 2nd row is clearly one of the Romancing SaGa games.

i think, the fifth in the second row is Ghost and goblins... remmember the part when you finish the game,, the princess appear and start once again...

I think the upper rightmost might be Parodius -- she's riding her fan like Koitsu does his paper airplane.

Looks like Goemon DS in a lot of these.