Roy Halladay's an eight-time All-Star, which seems like a lot. Especially considering that Greg Maddux was an All-Star eight times.
Halladay's got a ways to go to catch Tom Seaver, though; he was an All-Star twelve times. And if Halladay somehow catches Seaver, he'll still trail Warren Spahn and his fourteen seasons as an All-Star. And remember, the rosters were significantly smaller in Spahn's day.