Sonic VS Super Mario
It depends on the game we're comparing. There are some Sonic games that are direct rip-offs of Mario, such as the Sonic Tennis and the Sonic game that replicates Mario Party (I forgot the name). Plus, in my opinion the Sonic games took a nose dive and now they all suck. Sonic turning to a werewolf? Good one!
The old Sonic games were great but the old Mario games were even better, and they still come out good.