I've got the old Microprose version of MTG back from the 90s. The people at slightlymagic redid that one and added a bunch of the newer cards, though unfortunately the AI is not that great, particularly with the ones that were community added. They do have some really good 'challenge modes' where the AI will start with various advantages like free creatures, extra life, and so on. I haven't played it for awhile, but it's a lot of fun. They also have an rpg-like mode called 'Shandalar' where you get a crappy starter deck and walk around playing for ante against various AI opponents, collecting gold to buy cards, and so on, but the community hasn't modded that part with the new cards at all.