Considering that the leading scorers on 2004 Detroit looked like this:
1 Richard Hamilton 17.6
2 Chauncey Billups 16.9
3 Rasheed Wallace 13.7
4 Tayshaun Prince 10.3
5 Mehmet Okur 9.6
6 Corliss Williamson 9.5
7 Ben Wallace 9.5
8 Mike James 6.3
9 Chucky Atkins 6.2
10 Elden Campbell 5.6
I'd say that it's 100% fact to say that "at some point during his career KG could have been the best scorer on a title team." Heck, looking at that he'd still have a shot (a very very long one) at still being the leading scorer on a title team, as long as there's 4 other starters in the 12-15 range (I don't see KG averaging more than 16-17 ppg at most for the rest of his career), and some bench players in the 9-12 range.
In general, though, I'm in the camp that from this point on, KG doesn't realistically have a shot at leading a championship team in scoring, but that from his rookie year to 2008 he definitely could have been, with a couple different roster moves, etc.