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As great as the selection of formerly exclusives was on PS2, I wouldn't play these original versions on PS2 again, when there are enhanced versions available. So MGS2: Substance and MGS3: Subsistance instead of the original versions for me, preferably with a HD upgrade.
I love to play some classic PS1 titles once in a while, but I can't stand them on a big TV anymore... I like them much better on a PSP or Vita screen.
So the reasons to keep a PS2 or PS1 connected to the TV are fading away, when you also have a PS3. And if Crisis Core and a few other PSP titles finally get Vita compatible, I can put my PSP in retirement, too. PS3 + PS4 connected to the TV and a PS Vita "on the go", and you are set up for 99% of all playstation games.
MGS 2: Substance HD (PS3) > MGS 2: Substance HD (Vita) > MGS 2: Substance (PS2) > MGS 2: Sons of Liberty (PS2)
MGS 3: Subsistance HD (PS3) > MGS 3: Subsistance HD (Vita) > MGS 3: Subsistance (PS2) > MGS 3: Snake Eater (PS2)
God of War 1 HD (PS3) > God of War 1 HD (Vita) > God of War 1 (PS2)
God of War 2 HD (PS3) > God of War 2 HD (Vita) > God of War 2 (PS2)
Devil May Cry HD Collection (PS3) > Devil May Cry 1 + 2 + 3 (PS2)
Final Fantasy X HD (PS3) > Final Fantasy X HD (Vita) > Final Fantasy X (PS2)
Ratchet & Clank Collection HD (PS3) > Ratchet & Clank 1 + 2 + 3 (PS2)
Shadow of the Colossus HD (PS3) >> Shadow of the Colossus (PS2)
ICO HD (PS3) >> ICO (PS2)
Persona 4 Golden (Vita) >> Persona 4 (PS2)
Jak & Daxter HD Collection (PS3) > Jak & Daxter 1 + 2 + 3 (PS2) > Jak & Daxter HD Collection (Vita)
