Bold statement:
The only song in the Di'Anno/Bayley catalogues that Bruce DOESN'T sing better than the original singer is "Remember Tomorrow" (I hate his "AH-ah-AHHA!"'s). That's not a dig on either Paul or Blaze - I LOVE Di'Anno, I really like Bayley - but c'mon. Bruce is one of the best metal singers that ever lived. It's not really a fair comparison, because it was live, but seeing "The Sign Of The Cross" on the Legacy tour was transcendent moment for me. It's one of the moments I was really looking forward to, and it delivered.
Maiden is a singular band; they have a style, they have a sort of... expectation. Just because you're not the right guy for MAIDEN, doesn't mean you're not a good musician. Plus, I understand from sources I trust that Blaze is a top notch human being too, which goes a long way. He just wasn't a good fit for Iron Maiden. No crime in that.