I dont know that I care where the talent came from, I do know that from top to bottom there is no heavyweight division with more depth.
I dont know why people keep bringing Barnett up, the guy doesn't even have a license, I seriously doubt he's ever going to fight in a sanctioned event in america again(sadly). Overeem's good, Id love to see him in the UFC but Aleksander is lacking and doesn't even make the top 15 of HW fighters by most accounts.
Regardless you're still cherrypicking the top of other promotions, lets compare heavyweight division to heavyweight division and I think you'll see that even with the holes it has the UFC is the most complete HW division in MMA.
You can rank Barnett if you want there is just no point to it IMO, Fedor and Overeem belong in the top ten but that leaves 7 fighters (IMO) from the UFC and as you move farther down the list its almost all UFC fighters. In the top 20 id say there are 8 non-ufc fighters and the only reason why this matters is for a fighter to move up or keep his ranking (if you're big on rankings) is to fight another ranked fighter.
Consensus Rankings posted July 29, 2009
Rank Fighter % Promotion Last Rank
1 Fedor Emelianenko 100 M-1 Global 1
2 Brock Lesnar 94 UFC 5
3 Josh Barnett 92 ??? 2
4 Frank Mir 86 UFC 3
5 Antonio Rodrigo Nogueira 83 UFC 4
6 Randy Couture 79 UFC 6
7 Shane Carwin 64 UFC 7
8 Brett Rogers 63 Strikeforce 8
9 Andrei Arlovski 58 Strikeforce 9
10 Alistair Overeem 56 Strikeforce 10
11 Cain Velasquez 43 UFC 11
12 Jeff Monson 37 Free Agent 12
13 Junior dos Santos 32 UFC 17
14 Fabricio Werdum 31 Strikeforce 14
15 Mirko Filipovic 28 UFC 13
16 Tim Sylvia 26 Adrenaline 15
17 Cheick Kongo 22 UFC 16
18 Ben Rothwell 21 UFC 19
19 Roy Nelson 20 UFC 24
20 Gegard Mousasi 19 Strikeforce 22
IMO it's a monopoly and often works against fighters but thats life I guess.