One of my recent personal favorites is Animal Crossing: New Leaf (3DS). I sunk 180+ hours into it last summer (it also distracted me from playing SMT IV, which is why I haven't gotten around to finishing it yet
), I really enjoyed it, though I've found that after a while there's not too much to do. Some people do find the pace to be a bit slow though. It's obviously not a super-realistic life sim, but I find it fun and very relaxing. It's fun to play with friends too.