Everyone loves a tournament arc.
Maybe you could do something with a certain criteria to enter, like sub and page count, then make a huge tournament bracket. For the first few rounds it can just be voting, but then the last maybe 16 comics each versus could get a dedicated thread with forum users voting. But the criteria for a vote to count would be that you have to have read both comics and write a few sentances explaining your vote. This ensures somewhat fair judgement while also outsourcing judging to the general forum instead of a few overloaded people. At the beginning of each thread, you could also update the image with the tournament bracket, building hype.
I know there are flaws to this approach- for example, being paired up with a super popular comic right off the bat, or that it would still be somewhat a popularity contest, but there are some good points, too.
I think having two comics against each other each time would help people decide on one instead of being overwhelmed with choices.
Having the individual threads and discussion could draw attention to all the comics, even if they lose.
Having the tournament style and general forum user participation in judging could build hype and make people more invested in the results and more likely to read the winning comics.
Making it so that people have to read both comics and write an explanation to vote could help mitigate the advantage that already popular comics could have.
Would like to hear if anyone else has any thoughts on this approach. Maybe additional rules or flaws I didn't forsee?