I’ve had good experiences emulating PS2 on my Steam Deck. PS3 I haven’t gotten anything to run well enough that I’d call it enjoyable. Some don’t run at all
It's also worth noting that even Sony can't be bothered to properly emulate the PS3, which has resulted in many PS3-era games being remade into either native PC versions, or PS4/5 titles.
While it's true that there are still some PS3-exclusive games that aren't available in other formats, many of them are, so most people can get pretty far without needing PS3 emulation.
I only bring that up for anyone that may think they need PS3 emulation, but maybe haven't been made aware of newer remakes or native PC ports of the games they're actually looking for.
Going by core count alone is a pretty shitty metric for CPU performance. The 4 core APU in the steam deck will outperform an 8 core bulldozer cpu by any metric
I'm gonna blow your mind by telling you there are already working PS4 and Xbox One emulators, although both only support a small number of games so far
PS3 and Xbox 360 can be emulated very well by a modern PC, the majority of games work without glitches
PS3 is the trickiest. They had that weird Cell architecture which is more difficult to emulate than simply "less-powerful x86" emulation required for more-recent consoles.
To be fair, PS2 emulation is still not that great, but I guess it's due to sheer amount of games for that system. Last summer I decided to check the PS2 emulation after 10 year break and 2 out of 3 games I tested didn't work properly. Granted, those are kinda niche games (Transformers (2004) and Free Running), but compatibility still needs work. Hardware requirements are decently low for the games that do work, though.
That's the one drag for me about the PS5 contrllers, the battery life before recharging. The PS3 controller did great, but the PS5 ones have so many features built in they die to quick for my liking.