The comparison between the two generations begins with the PS2/Xbox generation. During that time, there were a variety of reasons to own both systems - there are always reasons to own a successful video game platform - and for most avid gamers, those reasons were obvious.
The Xbox was the more powerful console and its relatively familiar hardware was similar to PC, which paved the way for many great FPSs. And we're not only talking about exclusives like Halo; we're also talking about most all multiplatform FPSs, which were typically best played on the Xbox.
In general, multiplatform games really were slightly better on Microsoft's machine, simply due to the ease of development and the added power the PS2 didn't offer.
At the same time, the PS2 was following closely in the footsteps of the original PlayStation and attempting to steal the original console's crown of "King of the RPGs." If you were an RPG fan, there's no way on earth you could only own a Xbox; the PS2 was an essential piece of equipment. And because the vast majority were exclusive to that system, role-playing fans simply didn't have any other alternative.
It went far beyond the Final Fantasy franchise - as any avid RPG follower knows - and despite Square-Enix and other developers tossing the occasional bone to Microsoft and Nintendo, we RPG fanatics knew the truth of things. If you didn't have a PS2, you simply weren't a fan of the RPG. We could factor in other genres at this point, but let's just say the PS2 had a far bigger and more diverse library.
Now, fast forward to the new generation. This time, Sony has the most powerful machine, and despite the massive installed user base of its predecessor, the PS3 has to start from behind. This reversed role shouldn't really have any effect on the software, but the power reversal may have had some impact. Look at the situation now: we have no idea if Bungie will do a Halo 4 (doesn't appear to be the case), and the two biggest FPSs on the horizon are PS3 exclusive: Resistance 2 and Killzone 2.
They're also franchises, which means sequels are almost inevitable. On the flip side, RPG fans are looking around going, "hey...where are the RPGs?" Yeah, they're not here, but check out the Xbox 360. Lost Odyssey, Blue Dragon, and the upcoming Infinite Undiscovery and Star Ocean 4.
...what the heck happened? Suddenly, two genres that are almost polar opposites of each other (just don't tell that to Deus Ex) are suddenly represented very differently on this generation's consoles from Sony and Microsoft. Everything is all switched about! Many will argue they'd still rather play FPSs on the 360 due to the "better controller," but that's becoming more and more of an opinion rather than fact, and let's not talk about The Orange Box.
That's just Valve and EA being lazy in regards to the PS3. Furthermore, in regards to multiplatform games, it's becoming inevitable that PS3 versions of games will be better than their 360 counterparts before long. The PS3 is simply the more powerful machine and now that designers are beginning to use the system as their debut development console, the day of the crappy 360-to-PS3 port is just about gone.
So, as far as I can see, the software roles for the PS3 and 360 have switched, at least so far as the FPS/RPG comparison. It's kind of bizarre, actually. I'm sitting here with both systems, and I'm anxiously looking forward to several potentially awesome FPSs for the PS3 and several potentially awesome RPGs for the 360... and the whole thing is just weird. Who'd a thunk it? More PlayStation 3 News...
i never noticed it but your right! too bad because i love rpg's but i also love fps. what i love more is when both come together, kinda like resistance 2 or call of duty, fat from an rpg but just the fact that you can go online and kinda lvl up in a certain way to get better guns are stuff is really great but i will miss out on that too human title, good thing theres diablo 3 and space siege for the pc