Gen1 - good for the most part. A few uninspired designs and a few I plain don't like. Gen2 - good again for the most part, but probably more that I don't like than Gen1. Gen3 - awesome for the most part. A few bad ones but mostly good. Gen4 - ok for the most part, but quite a few I don't like, and a real lack of ones I really love. Gen5 - mediocre. Plenty that I love, but also a whole lot that I can't. Totally different feel to the other Gens. Gen6 - so far, so good. Only two or three that I don't particularly like, and the rest I pretty much love.
I'm pretty much in the same boat as you, TC, just with 6 and 2 flipped, and apparently for different reasons.
Gen 6 could either drop or rise, depending on what else shows up. I'm not including my opinion on megas, though I think they'd kind of be a wash for me anyway. For each one I don't like, there's one I like a lot.
Gen 2 and Gen 3 are kind of similar to me in that they have a lot of designs I'm indifferent to mixed in with the ones I like and the ones I don't.
Gen 4 and Gen 5 have the opposite issue, where they seem split almost in half between designs I really like, and designs I dislike, with very little that I'm indifferent to.
I like almost every Gen 1 design. Clefable is the most notable exception.
Gen 6 - Every single design is a gem so far. The only one I really dislike is Pyroar Female. Gen 3 - A lot of good designs, very few which I dislike. Gen 5 - Also a lot of good designs. Less than Gen 3, but still plenty of great ones. Gen 4 - Rotom. Gen 1 - This Gen is good, but loses so many points because of Jynx Gen 2 - Nope. A few designs stand out, but there are just too many I'm indifferent too.
Personally, I feel that Gen III and V struck the perfect balance between simplicity (I and II) and complexity (parts of IV). The reason I rank III above V is because I vastly prefer the starters and legendaries of the former.
Between Gen I and II, I just happen to prefer the designs of the latter (especially legendaries, though I don't care for the starters).
Gen IV has my least favourite individual designs (i.e. Rhyperior/Dialga/Arceus), though I like the rest of the dex enough to put it above Gen I.
It's all fairly close regardless; I can't really understand disliking an entire generation of designs.