Hopkins would outclass him. No disrespect to McClellan who paid his dues too, but Hopkins would outbox him and after the 9th or 10th rounds probably stop him.
Hopkins. Too intelligent and versatile, especially against the post-Steward McClellan who became sloppier and too in love with his power.
If they had fought in 1993 or so though, then G-Man's chances increase. I feel Hopkins improved after that and hit his prime in the 1996-2001 period.