to be honest i'd like all of these games, Sony needs to give Uncharted and Killzone (and all the games they're releasing) a break and release these games.
Warhawk was great, still one of the most enjoyable online games ever, its fun, frantic and very skill based, if they made another one in space with Battlefront-like gameplay it will be even better (but please keep the split screen online!) , imagine having huge(er) levels with battle combat, air and space all in one map
Syphon filter as explained above.
The Getaway games on PS2 had a great storyline and characters, and also great cover systems, though i'd argue i liked the storyline of the first than Black monday, but Black Monday had more characters to play with , the first also had more realistic feel to it, it has a huge potential of getting even better, keep the realistic element, and also the british accents 
i learned a lot of british slangs (mostly dirty ones) from this game 
Eight Days seems to be a lot like The Getaway, so i wouldn't mind if they rename it the Getaway 3 : Eight Days a Week , staring Beatles and the lonely heart club band
As for Sly 4 its obviously coming (even though thats not really a first party Sony game)
