I don't think that playing any two from the button is correct in heads-up hold'em. By limping, you're telling the other guy that you're weak, which opens you up to a raise. So much for your 3:1 odds. Also, there are plenty of scenarios where one hand is more than a 3:1 favorite. Any pair is about a 4.5:1 favorite favorite over a smaller pair. Any pair is a prohibitive favorite against two under-cards.
In stud variations, there can be much bigger differences in hand values than in hold'em because, well, you start with three cards rather than two. Taking high-only stud first, 222 is a huge favorite against AAK. Rolled-up trips against something like 973 is a ridiculous favorite. A decent pair against three random cards is a pretty big favorite. And so on. In razz, if you take a three-card Six against KKK, you can hardly lose. You can find similar scenarios in stud/8. Go to
www.twodimes.net/poker and play around with different scenarios.