I mean the Sonic IP is obviously very recogonizable and we all like Sonic, but his character brand is maybe 1/10 as valuable as Mario. just saying. Not nearly as resilient or powerful as Mario in terms of market relevance, and this is coming from someone who likes Sonic games generally speaking
he is definitely one of the most recognizable characters though. the problem is that there haven't been many good Sonic games in a while- his relevance is definitely dramatically less than what it was 10 years ago. Also in terms of sales no Sonic game has ever breached 5 million and in the recent years many of his titles have failed to even break 1 million :/ just saying
I think it says a lot that the best selling 'Sonic' game ever is the "Mario - Sonic Olympics" Wii game. one could argue that competing against Mario (and therefore the Mario connection) is a big part of Sonic's relevance