5 fps is not "just fine". Something approaching full speed is "just fine". All 5 fps does is prove my point precisely. The job requires more horsepower than is currently available.
You'd make good upper management with those sorts of long-term thinking skills.
Plenty of games in MAME weren't playable 5 years ago. A combination of better programming and exponentially increasing hardware means they are today.
The PS2 isn't dead. Far from it. Sony will support it officially for some time yet as a budget console (the PSOne was available up to 6 years into the life of the PS2!).
The fact that someone is working on a PS2 emulator *now* is a "goof thing" (tm). Buy the time the PS2 is officially dead, this project will be in it's prime.
Furthermore, PS2s are utterly rubbish pieces of hardware. I've still got my original Sega Master System, and I'm sure it's still got a few more decades left in it. PS2s go pop after a few years thanks to their crappy design and underpowered lasers. As far as being a collectable item in 10-20 years time, I doubt these things will honestly last that long. I *hope* that the Chinese spare parts market continues to deliver replacement laser units and whatnot for them like they occasionally do for Dreamcast today.
But in terms of forward planning, an emulator running at 5FPS today is just fine. Think about it in terms of a few years/decades from now, instead of merely as a replacement for what you have today. Software development (especially development that is done for free by individuals in their spare time) takes a lot of time. 5FPS is 10FPS next year, and 20FPS the year after, and so on.
Again, look at MAME, Chankast, etc etc. Hell, when I first started using SNES emulators, none of them would play properly on my desktop hardware. Now mobile phones have enough grunt to play them. These things take time, and need to start somewhere. You can't criticise them for that.