I've always hated this Jak VS Ratchet argument, It's like the Crash VS Spyro one. They are two different games to one and other to get compared to all the time. But just to contribute to the thread. I like both franchises. But I prefer Ratchet a lot more. probally because I've played and completed more games in that franchise.
I am a big Ratchet & Clank fan. I adore the PS2 games (aside from Gladiator) the most but I enjoyed the PS3 ones too, Crack in Time especially. I love the gameplay, I love the crazy, over the top weapons and I love the locations and different planets you explore. Ratchet 2 is probably my favourite, but I loved 3. Never played Size Matters, Secret Agent Clank, All 4 One or Full Frontal Assault.
(Shameless promotion: I did a playthough of the first one and I plan to do them all)
And I also really like the Jak games too. I didn't get far into 1 or 3 but I played the hell out of 2. I don't see why people say it's the worst one. Surely that racing one is?
Naughty Dog need to make a new Jak game, I didn't play the PSP one but I heard it wasn't amazing. Forget the HD remakes, I want to see Jak 4.