I really don't believe there were ever 'old days' when Peter was the main character. Imo, season one focused equally on the core 7 characters; Peter, Claire, Nathan, Matt, Niki, Hiro and Mohinder. These days it's basically the Sylar show. Not that I'm complaining.
kinda, tbh back in 'the good old days' peter wasnt really my favourite, but these days I like him a lot more, and its a shame when I dont see him as much, but I think its important to focus on the other characters storylines as well to get Mehr variety