Ignoring all the tech specs...
Here are a few of the reasons why i like the Megadrive:
Toejam & Earl
Streets of Rage 1 &2 (they cocked up the European release of SoR 3
Phantasy Star games
Shining Force 1 & 2
Robocop VS Terminator
Mortal Kombat 1, 2 and 3
Vectorman 1 & 2
Splatterhouse 2 & 3
California Games 1 & 2
Golden Axe 1, 2 & 3
Road Rash 1, 2 & 3.... and many many more.....
Now for some games i like on the Snes:
Final Fantasy 2 & 3
Secret of Mana
Secret of Evermore
Breath of Fire 1 & 2
Shadowrun (the Megadrive version looked better but i prefer this one
Zombies Ate My Neighbours
Weaponlord.... and more!
Some people may think some of these games are crap but i liked them
there are loads more i enjoyed on both platforms but cannot be bothered to think of them all
I did not mention Mario as i've not enjoyed it since Super Mario Bros 3 on the old Nes