The AHL team only survives because it is convenient for MLSE to keep them alive as it makes their hockey ops work better and they have a deal to manage/use the Ricoh. On a stand alone basis, as an independant hockey team needing revenue to survive....there is no way that you could describe what Toronto does as "supporting" the Marlies.
The GTA has no reason to be proud of its Junior hockey support either. Annually, the battle for the lowest attendance in the O is a two horse race between the Brampton Battalion and the St. Michaels Majors of Mississauga. Last year it was won by Brampton (actually tied with Erie), the previous year by Mississauga. Last year's attendance in Mississauga was boosted by having the number 1 ranked (for most of the season) team in the country and the ability to tie season and group tickets to attendance the memorial cup....even with those factors, the Majors barely got their attendance to average over 3k per game (the 50% full 50% empty mark).
http://jrhockeyrecruit.com/2011/05/ohl-2010-2011-attendance-report/
These two teams survive because they have rich and passionate ownership......not because of any great outpowring of support and ticket sales. That huge sigh of relief back in March was because the Owen Sound Attack made the Memorial Cup....their fans travel and they were the ones that gave the Mem Cup ticket sales a late boost to the point they almost sold out (they didn't but they got close enough that it did not look too bad on TV....average attendance for the 9 games was about 5,300).
The Gens do better but this should be noted....in what should have been a banner year for GTA OHL attendance (still a relatively new rink for the Gens with a pretty good team....and best team in the country with the Mem Cup to market in Mississauga) the combined average attendance for the three teams was 8,734! Not only is that lower than, say, London.....if you compare it to other cities (obviously smaller than the GTA) who have both the NHL and the CHL (these are the 2010 figures for these teams unless noted)....Calgary - Hitmen average 8,478....Ottawa - 67's average 7,499.....Vancouver - Giants average 7,117.....Edmonton (2011) average 4,085.....I can't find numbers on the Montreal team that plays in the old Verdun arena (if you ever get a chance to watch a game there do so!).