Same here. I never in a million years thought I'd ever play a lead when I first picked up a guitar. Even after the first few years, I refused to venture into that realm. I was happy just being a rhythm guitarist. Over the past 4 years, I've been pushed into the capacity of a lead guitarist more out of necessity than because I wanted to (i.e. "You've been playing guitar longer than he has, so you're the lead guitarist") I don't enjoy it as much as being able to just write riffs and I am by no means a shredder. But I think I've handled the duties well.
I'd like to think that I have a knack for writing melodic riffs and hooks that have a good edge to them and I pride myself on that. That has become my primary function in the band I'm with now along with having lead guitar duties thrust upon me and I'm quite happy with being the primary songwriter.
What inspires me to be my best? Hearing people applaud and cheer after we play a song I've written or have had a hand in writing is inspiration enough to continue on.