The Wikipedia mobile client is a Phonegap app. But it, and most such apps, are basically more-elaborate Web wrappers around a Web site's content. While they might adequately not offend each platform's conventions, they are not exemplary w.r.t. platform UI capabilities. It would be very hard to make a cross-platform app that uses Fragment and multiple layouts in a way that really captures the power of those UI capabilities.
I would hardly call the current Wikipedia app 'best' - it is rather quite terrible. I'd know, since I wrote most of it :) We're rewriting it all to be completely native now.
It was one of the few widely used open source Phonegap apps I could think of. I agree going native is the right answer. There are some cases where a cross-platform app is the right answer on all platforms, but that's a pretty narrow set of cases. If an app is fairly popular, it's worth doing a native implementation.
