I've done the same. A few months back played the first 3 in the series. Not as tough or as pretty to look at from memory of early Xbox days but still decent games.
Worst of the 3 I think was Pandora Tomorrow. I've now finished up to Double Agent. I think Double Agent had some good ideas and the game could have been great if it was for how clunky the game felt and the endless bugs. Being on PC, I obviously changed the game to fit my resolution, but in turn this can create constant crashes and even messes the game up so much that I was unable to activate the final cutscene. I like the decision making aspect of the game but the game was just messy overall.
I'm now on Conviction and boy I wasn't ready for this. This game feels like it promotes killing everyone you come across. Movement is stupidly accelerated, doesn't feel like a game to sneak in like the previous games, the new cover system just adds to the idea of eliminating everyone. I'm not a fan of how they have changed the game.