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Exactly, if it doesn't work it doesn't work It's worth a try anyway, even if it is really slow, at least we can work from there and/or wait for more advanced device.

I doubt we'll see a full speed PSP emulator, the PSP is too fast. The n900 is faster, but only someone like sony with full knowledge of the technical workings of the psp (unless that information is publicly available) would have a shot at it.

You typically need at least an order of magnitude more cpu performance to emulate a system at full speed, and even faster than that would be good to handle corner cases.
PSX should be possible to emulate at full speed. N64 will probably see high level emulation only. Dreamcast may see partially working high level emulation, and that's probably as far as usable emulators on the n900 will go. Nintendo DS will eventually be emulated though.

probably a good chance for Wii emulation then?

considering that dolphin runs wii-games on computer with playable framerates, i think its not impossible, but unlikely.

Sure, a wii emulator could work if you have no desire for real time performance.

Dreamcast ran a piddling 200Mhz SH-4. The SH-4 was basically an SH-3 with a SIMD unit (3dnow, sse, etc) bolted on. The SH-3/SH-4 are from a generation of microprocessor design behind the Cortex A8 used in the n900. Not sure if the results are comparable, but the Dreamcast's SH-4 was rated at doing 360MIPs, while the Cortex A8 @ 600Mhz in the n900 is rated at 1200MIPs, so there's a healthy advance in performance there. (the n900 also has a faster, more featured gpu, but I dont' think that's as important for emulation)
The Dreamcast also did around 1GFlop, compared to around 5GFlops for the OMAP3430.
(N64 was 125MIPs, 100MFlops for comparison)

The gamecube/wii cpu is in a different class entirely, its design is more comparable to the cortex A9, and it runs at a clockspeed comparable to the n900 (around 500mhz on the gamecube, 700-800mhz on the wii).
Gamecube's cpu did around 1000 MIPs and 2Gflops, so it's too close to the performance of an omap3430 (and the wii cpu is clocked even higher). Plus, it used out of order execution, which is a cpu feature that basically gives higher efficiency/utilization. (probably up to 25% better than the specs indicate, though it seems that it helps unusually obtuse architectures, like x86, more so than straight forward ones like arm and powerpc, but the cortex a9 is getting about a 25% boost over the a8 from including OOE)

While I'm at it, PSP has a 333Mhz R4000 based cpu, capable of 2600MFlops. I can't find any statistics for its MIPS (millions of instructions per second, btw) rating, but it has a similar cpu to the n64 at ~3x the clock speed, so around 400MIPS sounds right.

A 3.2Ghz Pentium 4 did about 10,000 MIPS, as does the primary cpu of the Cell processor. A 500Mhz Pentium 3 did 1354MIPS, which is a bit beyond the Cortex A8 (though the A8 has a more powerful FPU/SIMD unit).

The A8 does 2 instructions per hz, the A9 does 2.5 instructions per hz, Pentium 3 did 2.7, Athlon did 3 and P4 did 3, Athlon 64 did over 4, and the most recent pc cpus are doing over 5 and close to 6.
At least in canned benchmarks, in actual performance cpus typically don't see anywhere near that level of performance on average. From memory, pre OOE x86 pc cpus did about 0.3 instructions per clock, and OOE cpus range from a bit under 1 instruction per clock (on average, with the Pentium 4 being one of the worst performing OOE designs per clock in actual performance) to approaching 2 now.

You guys are forgetting that the PSP also has a 300 MHz DSP to compliment the 333 MHz CPU.

edit: Check out the tech specs - Wikipedia link

Is the dsp even used for games, or just media? Anyhow its the same isa as the other core at the same speed with some dedicated video decode hardware.

You not compare diferent processors basead in MIPS. these comparations not prove nothing in the question of what processor is more fast.

motive:
One processor use one instruciton to do a job, other processor need more instructions to realize the same job.

Note: MIPS, Clock speed, Quantity of poligons per second, are horrible forms of compare performace indiferent processors, and not the correct form of compare diferent processors performance.

psp kills n900 on the gpu- the n900 cant even compet on hardware so how can it emulate

dont worry about anything else- its irrelevant if you havent got the 3d capabilities