Eh, well, haven't gotten it yet, however, I do know what it comes with.
Super Mario Allstars comes with the game disc, of course. It's a direct port of the SNES Super Mario Allstars, so you get Super Mario Bros., Super Mario Bros. 2 (Super Mario Bros.: the Lost Levels), Super Mario USA (Super Mario Bros. 2 in America), and Super Mario Bros. 3. These games have updated graphics, originally in 8-bit, re-vamped to 16-bit.
It also comes with a soundtrack and a 60-page history book of Mario.