Hampton always loses his first game (exception was last year w/ Colorado, I believe).
That said, he had a pretty bad year last year, even considering Coors Field. The logical explanation and the unfortunate news for Mike is that he's always been a better pitcher at home than on the road - he dominates at home, is average when away - not exactly what you want when your home stadium is Coors'.
So my answer is yes, he is a better player than you rate him, imo. But frankly, what we feel and how he actually does are two different things. To be honest, I don't know how you rate anyone who plays in Colorado (let's face it, Todd Helton is not as good as Coors Field makes him out to be).
You can't start rating based on home field, that's too subjective - so rate Mike the way he performs, that's all we can expect of you (and I'll bump him back up the great pitcher he truly is on my own time
)
$.02