GB’s has the best cheeseburger. Any of them.
However, since COVID, they clearly started freezing their meat, like many other places have been doing. Since then, JB’s in TianMu has the best cheeseburgers.
Chili’s and TGI Fridays always makes a reliable burger. The Diner is great, too.
I mean, heh, these are all non-Taiwanese places (unless The Diner counts, but pretty sure they’re foreigners), but you asked! I haven’t yet to find “the one true” burger made by an actual Taiwanese brand. Even if you do find one, it’ll be served with Kraft fake cheese and 5 lbs of iceberg lettuce. EDIT: Branched off: