Exactly, Blade 2 & especially Mimic aren't the best representations of his work... but it's usually the case, that is all people have to go off. I think Hellboy was by far his best work... in Hollywood at least, he is extremely resourceful & knows how to stretch a budget. He has such unique style of shooting that makes his work such a spectatcle to watch & he has such a passion for his work, just listen to the DVD commentaries on Blade 2, the Devil's Backbone & especially Hellboy.
But as far as X3 goes, GDT doesn't seem to be that interested in the series.... I think he said he'd review the offer if Fox ever approached him for a X-men/Spinoff movie, but it'd be unlikely that he'd do it. Anyways considering how stacked his schedule is for the next year or so, with him shooting Pan's Labyrinth in Spain, starting pre-production on Hellboy 2 early next year & perhaps doing 'At the Mountains of Madness' for Dreamworks. So, I don't think he'd accept if he was approached, though who knows.