(Nothing: 0.12% - 3) - what kind of games are we talking about ?

[TWIST_OF_HATE]

From compatibility overview. Just interesting ))
And why those games still impossible to emulate ?

[Kian Stevens]

Exactly what you said: Compatibility.

PCSX2 attempts to take one instruction set, the PS2's, and convert it into x86. This works most of the time, but not all.
That could be because of anything, like how the emulator's been programmed, how the games have been written, or how the code is compiled. The games are native to the PS2's original hardware and instruction set, and not native to software that'll convert it to x86.
It's not impossible to emulate these games, in fact, every day these games are being worked on. If you look at prafull's patch thread (link below), he's took a bunch of games that were once under the 'Nothing' list and has made them work properly.

http://forums.pcsx2.net/Thread-Fixing-unplayable-games

[Konoko56]

Yes some games not work as they expect (intro and ingame included) and some have a custom patch to avoid big issue but it's a workaround, real issue is still here and hope they will be fixed.