Feel you fully on this one. Similar feelings myself.Gen 4 made me quit, (at least until Gen 5,) despite the introduction of many powerful Pokemon, I really disliked a LOT of their designs.
Few exceptions include Dusknoir and the two Eevees. It took a very long time for the popular Lucario to grow on me too.
The legendaries on the other hand were brilliant, especially Darkrai, but man I couldn't even start the game properly since I didn't like any of the starters.
By the way, I raise Pokemon base on their looks lol, and to me, Gen 4 is by far the worst.