In a word, none.
Let me explain. To be "worth" two credits, it should be "worth" two meals at a "regular" place.
Look at it this way, a regular table service dinner is worth about $45 give or take (at WDW prices). So to be worth it, a two credit dinner would have to be "worth" about $90 (again in WDW prices)
Now some two credit places are in the $60 - $70 range maybe, but none hit the full "double the value" of a regular restaruant.
To me, that means that none of them are "worth" spending double the credits. Now of course if you have an extra credit for some reason, or you really really like a place, that is a different story, but from a pure cost analysis, none are really worth it.
-dave