I don't try to surprass myself or any of my previous projects. Whenever I make a new story I don't think about how to make it better than my last, I just create something to my own pleasure or current mood/interests.
When I look back at the old projects and see some that could've been done better, I just go back and improve them or put them on "eventual reboot" list.
If someone would ask me "which work is your best?" I'd just give them a (long) list of my personal favorites saying "these".
I guess you can say my stats are a constant line with some bumps here and there, but no noticeable peaks or falls.