"I don't think this is good" - Can be jealous, but a normal opinion.
"I'm better than this" - Makes you sound pretty jealous.It's not really a helpful critique, and it tends to come from a place of 'I'm better, so why is this more popular?'
I think it's helpful to take a step back and say, yes, why? Is the artist amazing at social media? Does the comic appeal to popular themes or trends? Did it get a specific lucky break?
If you can look at those without bitterness, then I'll believe you're jealousy free. You can admire skill on social media skill, acknowledge when you are choosing to stray away from popular trends, and study lucky breaks without venom.
-'Ugh people only read this because the author's popular' -> 'Wow! This author did an amazing job building a social media fanbase. Clearly I need to work on that'
-'I don't get what anybody sees in this! it's horrible' -> 'I don't understand the appeal of this. I should try and figure it out and learn from it, because clearly it's got something that draws people in enough to overcome its flaws'
-'Stupid fans only want manga style romance comics' -> 'Manga inspired romance does really well on this site, but I don't think I'd enjoy writing it, so I can accept my work won't follow trends and that means some people won't be interested'
-'Nobody would even look at this garbage if they hadn't gotten that big feature' -> 'That feature really helped this comic take off, despite it's weaknesses. I wonder if it would do the same for me'
'Why is this shit popular?' isn't always a jealous question, but it's almost always a resentful one. And following it makes you not just judge the artist, but judge their fans as shallow. It's fine if people like pretty art or sexy leads or big fights!