Matching memes that have been made years ago with recent memes just by # of upvotes doesn't work out well.
As the number of comunity members increases every year so does the upvote-power in total and 300+ memes are no longer a thing.
Which means the mere upvote count alone does not qualify as a famous meme ranking criteria over a longer time period.
Imho You have to divide the upvote count of a meme by the total upvote volume/traffic in that given year on whole imgflip.
e.g. a 2015-dated meme with 500 upvotes and a total of 500,000 upvotes on imgflip in that year should outrank an 800-upvotes-meme created in 2018 given 1,000,000 upvotes in total in 2018 because there were twice as many upvotes floating around in total in 2018 but the 2018-meme didn't aquire twice as many upvotes.
Plus the stream separation has an effect as well. Up to 2018 you might have a decent frontpage terminator with a 300+ upvote political meme. Thats no longer a possibility. Epic politics memes after 2018 would completely fall through the cracks of an imgflip famous meme ranking.
which is mainly why I quit my "hall of fame"-Top100 project mentioned above.
there would be need of separately calculating an upvote quotient for the politics stream in order to "make politics great again" on imglfip.