I'm just throwing an idea I had earlier today up here. Maybe someone will use it.
So, you have a game you want to make. Could be anything really. You wanna do console, PC, and Linux. Don't have funds to do all of it? What if you dev'd a game simply around it being just as fun on console as on an emulator. I'll use the PS2 as my example.
If there were to be a PC release of Persona 3 it would take a lot of work. But to make it run on an EMU wouldn't take much. Or even just a new game. Build it for an emulator! All the functionality of the console can still be there too, no worries there. If someone has a PS2 and wants to play my new Gran Turismo like racing game, they totally can. So can PC players. At that you could release DLC packs like maps and cars and whatever, but also graphics overhauls and shit. Dollar each, and no one is stopping anyone from making their own obviously, or at least I wouldn't, but 4K graphics capability at launch from dev for 4 dollars? I think thats a great idea!
Then during dev of games you could even release like a vulkan based renderer for the emulators or something. That would be super cool.
I dunno just a thought.
Ideal Consoles: PS2 PSP Wii / U Gamecube Dreamcast OXbox?
First of for using a PS2 Emulator the user (gamer) would technically need a legally obtained PS2 BIOS (which you can only get if you own a PS2 and extract it yourself which in turn technically breaks Sony's EULA). I don't know about the other platforms, but emulation is less then perfect to begin with (even PCSX2 which is arguably the best PS2 emulator still has stuff that it cannot do). Then there's the issue that not every emulator is available on all platforms (PSCX2 is, but you mentioned other consoles too), and so you'd have different compatibility depending on the platform (limited by the emulator(s) available).
Technicalities aside, there's no reason to do this. PS2 is a platform that's...... a few years old, graphics are more then just sub-par (assuming gamers don't look for graphics these days is a just simply blindsided). The gameplay could of course be fine, but you're still at the point of... why would you do this? Why waste time on an old platform that the user then needs to emulate...?
You also would miss out on any online-play possibilities whatsoever since the emulators just don't do it (last time I checked anyway, please correct me if I'm wrong here). Granted not every game wants online capabilities, but if you do, you're out of luck.
Why not just use a multi-platform engine to begin with. Unreal Engine 4, Unity, and to an extend CryEngine are all multi-platform and are free to use up to a certain point (you only pay for them once you start making actual money).
UE4 runs on (among others) Windows, Linux, macOS, XBone, PS4, even compiled in the browser. Unity has similar capabilities now.
I'm really confused on why anyone would do this. If you're just out for creating games specifically for those old platforms, OK fine whatever. It's bothersome but if that's what you want, OK. But just to be multi-platform? Nah.
/edit Specifically about Persona 3. I think what you are referring to is a port of the game to PC? There have been games that have been ported this way (it's what some studios do for Win->Linux Porting all the time). The Problem here is really licensing. Really the only viable PS2 emulator is PCSX2 (as mentioned above). PCSX2 is licensed under GPL and so they cannot publish the game with PCSX2 bundled without releasing the Source for the game itself. Which I think is clear why this isn't being done.
You angle this like I'm presenting it as a business idea. I know theres problems with it as a literal use but I highly doubt anyone will do it looking back at it.
Not really no, that's why I mentioned the free part. There is no reason to develop for an old platform, the development alone is cumbersome at best and it doesn't really give you anything.
Say you want to do this just for fun and a learning experience. For fun yes, sure, go for it as I said. But as a learning experience... maybe you want to pursue a job in the gaming industry at some point. What do you gain for developing for such an old platform? You may get some general idea of how development works, but you're getting no experience whatsoever in current gen techniques and engines.
Better take that time looking at current gen stuff and actually use it later on.
Idk, but that sounds like you think of it as a bad idea? Or am I just getting that sentence wrong
No I have been entertaining the idea of making a game around a story I've been working on and if I was gunna do one it would be done this way. Not sure though.
The thing is the audiance for something like that would be rather small (doesn't matter if it's commercial or not). I don't own a PS2, but I think homebrewed games only work on a geniune PS2 when it is "jailbroken" (even though that term is a bit newer then the PS2 itself ).
For an emulator sure it would work, but there we are again that people would first need to set it up. Setting one up isn't the easiest in the first place, then you need the BIOS for it (see above).
So yeah, overall audience rather small. But as I said, if it's just for fun and lulz go for it.
Natively developed for multiplatform using UE4/Unity would be the best way to go (also for practical experience), running it through an Emulator generally introduces a layer you have no control over (ok, technically UE4/Unity has that issue too, but you can modify a lot more there), and you don't know how the emulator might behave on different render settings, even if your code is "perfect" (which spoiler alert, it will never be).
I don't know about the PS2, but as far as I know the PS4 runs on a BSD base, soooo... yeah
Or am I just getting that sentence wrong 
).