Never tried EA Sports Active, but to put in an opposing viewpoint, I love the DDR games.

I got the Disney one, and then bought the original Hottest Party off of amazon marketplace (since it's no longer sold in stores). Largely b/c yes, I do like the song variety.
In terms of cost-effectiveness, I'd recommend getting DDR Disney Grooves first as it comes with two mats. You can then add on single titles (w/o additional mats) through eBay, amazon marketplace, etc. (Unless of course you want more mats; then stick with the bundles.) That's what I'm doing.
I have Wii Fit but honestly haven't used it at all in hmm three months or so. I get a better cardio workout, if that's my goal, with DDR. I wouldn't say the strength training on Wii Fit is a total joke (BW exercises aren't evil and actually I plan to focus on BW exercises after I finish OPT), but it's very easy to cheat, you can't plan your sets/reps, and I just found the interface irritating.
My brother also got Wii Sports Resort recently. Only played it for around 10 minutes, but it seemed fun. Relatively lowgrade activity, however, though I have heard of people really getting into tennis or boxing.