http://www.supermariobrothers.org/
Its a flash game, and ive played halfway through the first episode and wow...this is the best Mario game i've ever played! I use a PS2 controller to play it-it mixes SMB1-World with many different elements and with amazingly 'Nintendo-ish' level design. New weapons (the Billy Cannon firing Bullet Bills is hilarious) and the addition of Link, Metroid/Zelda 2 themed levels in certain parts (you fight Mother Brain in a Mario game!) it just blows my mind. Watch the trailer if anything else :http://www.supermariobrothers.org/smbx/