I started watching on season 9, so I don't really know about the joke acts before that, but from the few I got to know I would rank them:
1. Rylan Clark.- I genuinely enjoyed most of Rylan performances. sure, he doesn't have a particularly strong voice, but most of his vocals were fine, plus the way he performed made up for that. Definitely the most entertaining act of his season, and I like the fact that he reached until top 5.
(Gap)
2. Honey G.- Second place mostly because of all that she has achieved, and I actually like her performances as well, they were fun. Sure, there were a lot of more talented contestants that should've gone further than her, but that doesn't take away some of the creativity she had and how catchy some of her performances were just by spelling her name.
(Gap)
3. Blonde Electra.- I liked their audition. Sure, they were really annoying, but they were fine... I guess. Plus, they didn't last enough to really annoy anyone.
4. Stevi Ritchie.- I never liked Stevi, but he was ok.
5. Bratavio.- Just no.