Right now I'd say I'm mostly focused on collecting for PS3, PS1, and DS, in that order. However, my prioritization of specific consoles has changed over time. If you would have asked me several years ago, Dreamcast and PS2 were both my number one collecting priorities and the consoles I would have collected the most for.
In terms of amount of games, Playstation consoles dominate my collection by volume; between all four PS consoles, they make up probably close to hald of all the games I own which is at 1805 right now.