Son of a bitch!
I love both of these shows and I've no idea who I'm voting for as they're about as equal as you can get. It's drama vs comedy. For that reason I'm erring on the side of The Wonder Years. I love it's wonderful recreation of the 60's and history, truly awesome soundtrack and probably the sweetest childhood romance I've ever seen. And of course, the most iconic narration in TV history.
The Simpsons is/was brilliantly clever, very funny at times and heartwarming but it'll never match The Wonder Years, which was an epic love letter to the 60's and growing up.