PS3:5 games
XBOX 360: edit: 21, just found a few others
Blu-Ray 17 movies
HDDVD 25 movies

PS3: 6 (and I'm currently borrowing HS) now + 5 downloadable

+ about another 10 this year! (with my brother)

PSP: 12 + 1 more this year

6 blu-ray films, + probably another 6 -8 this year

N64 - 6
Xbox - 13
Game cube - 4
360 - 5. XBLA - 10
NDS - 15

I generally trade games in as soon as they are completed or am bored of them but during the last couple of console generation these are the approximate numbers:

Xbox360 / XBL arcade: 0 / 8

Gamecube 80+

DS: 60+

Wii: 18

PC: 2

I did used to keep all my games but now I only keep the ones I think I am likely to play again or have some reply value.
I still have the save files from the Gamecube and can always buy them again much cheaper than when I sold them.

@llewdebkram:

If you have traded the games in, they are no longer part of your attach rate.

PS3 games = 5
PS3 downloads = 7
Blu rays = 13

I don't remember the others. But for the Wii I have 9.

NES - 6
SNES - 20+
N64 - 13
GameCube - 16
PS2 - 11
Wii - 3 (VC - 6)

8 Famicom (NES)
20+ PS1
20+ PS2
10+ GC
1 (+ will get both Final Fantasy games and GT5) PS3
6 (+ preorders for galaxy and kart, will get Final Fantasy) Wii
2 Virtual Console
3 PC
4 GBA
4 (+ will get both Final Fantasy games) DS
3 (+ preorder for Final Fantasy CC) PSP
26 HD DVD movies
0 Blu-ray movies

Wii
10 retail (12-14 by end of year)
16 download (17-18 by end of year)

DS
15 (16-17 by end of year)