Personally I always felt that they were two very different games, Sonic was a flashy fast paced game that was mostly designed to show off the power of the Genesis. lots of colors and fast action.
While Mario was more exploration based, with hidden exits and stuff.

Its not like SF2 vs MK, Mario and Sonic are just different kind of games imo.

I always enjoyed Super Mario more. More of a relaxed way to play levels (except underwater levels haha)

Sega does what Nintendon't.

Sonic was cool to me as a kid and Mario was lame to me as a kid.

Fast forward today. Sega treats it's fans with respect and are willing to ask them to lend a hand when they need it.
Nintendo treat it's fans like garbage and will go after fanmade projects due to them knowing that if the fans can make a better game than them it'll ruin their image even though it's a fangame that is free.

Yeah being a Sonic Fan seems a better choice right now as currently Nintendo is being run by the same type of people at Disney.
And only the big IP's get all the dedication and effort with varying results.

Unless your Pokemon then you already know disappointment is always a thing with them due to them being run by people who don't want to actually work without realizing that putting effort into something you do will help you in the long run rather than being soulless or were trying but for some reason stopped midway cause the lazy.

I'm heavily biased since I've always preferred Sonic over Mario but I'll say Sonic

Mario may have more quality games (though highly dependent on who you ask) but Sonic beats him out by personality by a lot
Nothing against Mario but he's always been kind of safe/bland to me

Also simply for as clunky as they can be I still prefer Sonic games over Mario's, Sonic just has a lot more fun ideas and isn't afraid to try something new while Mario is scared to deviate from his Mario 64 semi-collectathon base

Mario.

Sonic also has far too many Mario levels which kill the speed. I never got the appeal tbh. Music slaps.

Also we never recovered from early DeviantArt.

Though it is better for memes

https://youtu.be/Nrk8sqZfsgI?feature=shared

Sonic

My calculus was always about abilities. This is only about Mario vs. Sonic from SNES/Genesis and prior systems. Nothing newer.

Mario: Run, Shoot, Embiggen, Stomp, Pick up/Throw, Swim, Tanookie Statue, Ride and Control Yoshi, Fly (Raccoon tail), Slide-attack, Invincible, and more.

Sonic: Run, Swim, Spin, Go Fast, Smash, Invincible. And that's about it, other than mini-games.

Mario is better, because he can do more. Sonic was just a high-budget Jazz Jackrabbit.

:ducks, runs serpentine from room:

Sonic.

Originally posted by Vox:

Sega does what Nintendon't.

Both SNES and Genesis/Megadrive had their things the other couldn't do.

Genesis couldn't even approach the colors or resolution of SNES.

Genesis could never have been capable of Uematsu's FF6 amazing soundtrack.

SNES could never do the speed of Sonic or EA's NHL games.

SNES could never have done the banger Streets of Rage soundtracks.

Genesis was never capable of the complexities of games like Civ, Sim City, or most RPGs.

Genesis could never have done Starfox.

They both had their trump cards, which is why both systems were successful.

Genesis had Phantasy Star IV which was pretty much on par with anything the SNES was doing in terms of RPGs.
In fact the only game that had similarly large sprite work in an RPG was Tengai Makyō Zero, and it needed an expensive co-processor to do it.

I've always liked Sonic more, because the older games focused on the story.

Mario is better.
There’s some incredibly subtle work done with the music,
which is still being used to this day.
You should read about it - it’s really interesting.

Super Mario Brothers 3 was when Mario Bros became REAL!

I prefer Mario. It’s simple and anyone could pick up and play it. I like Sonic games now bc of nostalgia and the soundtracks are great, but back then I never liked the idea of zipping through stages like that at light speed. It made it more difficult and I liked taking my time and exploring in games.