Same story for me as far as MMORPG's, Farmville and similar go. I get super addicted for a week and play probably 8 hours a day, then I just get bored. The whole thing is vaguely addicting, but ultimately completely uninteresting.
If I'm going to watch a character level up I'd much rather hit the gym. The increasing weights you can lift offer a nice chance for some nerdy analysis while you're also actually doing something useful.
I rarely engage in shameless self promotion, but this seems like an appropriate moment. My startup, Fitocracy, is built around the notion of loosely mapping the MMORPG experience to exercise and fitness. We've been getting fairly popular with the early adopter crowd and we've even been featured in XKCD and Penny-Arcade.
I'll chime in on this about how the gym worked for me. Do both strength training and aerobic exercise; both are good for you, and both will work to keep you healthy. I joined a gym that did CrossFit workouts which combines both styles of exercise, and have been doing so for the last 9 months.
I could never stay motivated at the gym on my own, whereas CrossFit is nice because it's run as a group class, and you typically have a coach that runs you through the exercises. It's a bit more expensive, but it's the only gym that I've ever actually stayed committed to.
As for results, I haven't lost any weight; but I've lost fat and gained a ton of muscle (it was extremely noticeable in my face.) I've also taken 2.5 inches off of my waist.
I've tried various methods, but a little notebook seemed to always work the best. Of course you can always transfer some data to a spreadsheet if you want a chart or something, but the only thing I really ever check is "the last time I did this exercise for this target reps what weight did I use and how many did I get?" Use that number to determine what to do today. Checking takes about 20 seconds. I now have years of weight training workouts in my little notebooks :)
I didn't really run any super advanced analytics. But when you're there 2 hours a day 6 days a week, it tends to stick in your mind when you're progressing and when you aren't.
But to give you a sense, it took me 3 years to go from 50kg to 64kg body weight (first ~8kg was in 6 months or so). 64 is my IBM limit so it's incredibly difficult to go up from that.
I could squat-lift 130kg, benchpress about 80kg, biceps curl around 25kg and so on ... it was epic.
I've since taken up boxing and in a way it's even awesomer.
I use a program called Beyond the White Board (http://beyondthewhiteboard.com/) it's $3/month. It's mainly built around CrossFit, but you could easily tailor it for your own workouts. Like a good geek, I tried to "roll my own" and use spreadsheets, but after 2-3 months I realized that the $3/month was a better usage of my resources.
If I'm going to watch a character level up I'd much rather hit the gym. The increasing weights you can lift offer a nice chance for some nerdy analysis while you're also actually doing something useful.