There aren't a lot of options and most of them aren't going to make you happy. Here are the ones I've tried:
- Magic Online (PC) - This is a PC game which may not suite you but it doesn't have hefty requirements (if you're browsing this website you can likely run it) but you do have to buy the cards. The upside is that it does all the rules for you and has a pretty slick interface (or at the least game part, the rest is blah).
- Magic: The Gathering: Duels of the Planeswalkers (360 XBLA) - This is a very simplified M:tG and it's decent if you're new to the game but awful if you have any experience with it. It doesn't let you actually build your deck, just add to the premade ones. It also has an incredibly frustrating 2.5 second timer after every action. It doesn't sound like much but when six effects fire off after every spell, that's 15 seconds of waiting per card. It sucks.
- Culdcept Saga (360) - This is a really neat game that is decent fun. It's a mix between Monopoly and Magic. The upside is it's incredibly cheap, the downside is the AI cheats like mad. I believe there's a PS2 version too.
- Eye of Judgment (PS3) - This is another neat card game but it's not well supported and instead of the AI cheating like mad, it essentially boils down to whoever goes first wins. I had bad luck with getting cards to recognize well, others had better luck. I don't know how easy it is to find cards for it but I haven't seen any booster packs for years.
If you're up to spending the money, I would say Magic Online. It has every Magic card and you can always find tournaments. The downside is you do have to buy your cards but you can get an excellent start by just doing the various types of drafts. If you're decent at the game you'll get to a point where the drafts pay for themselves by winning prizes.
Personally, I hated Duels of the Planeswalkers for the reasons mentioned above and just can't recommend it. Culdcept Saga might be fun if you have a buddy but playing against the AI is infuriating. Eye of Judgment was a neat concept but it just isn't that interesting of a game.