3 was easily my favorite storywise.
If only they would have had 3's story, 2's co-op mode, and a mix of the 1st and 3rds competitive...to start the series.
but I must say, Insomniac probably isn't the company that can push the franchise to its full potential. While I enjoyed them all and recommend the series, it was unfocused. All 3 are really different and feel like spinoffs to each other.
If the second team in Guerrilla Games picks it up it may have a future tho I doubt it happens.
Resistance: Retribution(PSP) was great too. It was made by Sony Bend(Uncharted: Golden Abyss and Syphon Filter series) I haven't played Resistance: Burning Skies(Vita, made by Nihilistic) but I did enjoy the demo. Too bad Sony Bend is too small to handle multiple projects.