Donkey Kong Country Returns is relentlessly difficult, while Kirby's Epic Yarn is relentlessly adorable.
I've played both, but I haven't played KEY all the way through. I can tell you that you would not be disappointed by Donkey Kong Country Returns. It's an extremely worthy successor to the old ones. Both are extremely great to play with a friend, though you'll eat up lives like crazy in DKCR that way (that's all part of the fun, though).
edited 20th Dec '10 9:12:13 PM by Enlong
I have a message from another time...From what I've played, DKCR wins. I like both but DKCR adds a challenge. Depends on if you want a challenge or not though.
Taking a break from FE1, for the FE8 draft insteadI'm going through this dilemma too.
I like to play games with my wife, but she's not a life-long gamer like I am. She played New Super Mario Bros. Wii with me, and that was fun, up to a point, because I was good at it, and it felt like old-hat, so I was able to blaze through things while she had to take a few seconds to line up a jump... Eventually, it almost boiled down into what Tycho from PA calls "Divorce Mode".
She's developing an interest in Minecraft, and has played The Sims pretty extensively. I'm thinking about getting one of these two games, and I'm leaning towards DKCR, if only because there's a challenge that will attract me... I'm worried it will put off my noob wife. However, she played a lot of Kirby growing up, and I heard that KEY has a multiplayer mode, too... So, I'm torn.
Frankly, I'd go for both, along with Sonic Colors. They're all pretty awesome in their own way.

I feel like a good 2D platformer...to those that have played both of these, which one would you suggest?