Always a fun topic - what were the best warships of class in WW2.
However, you really have to ask is when were they built. Otherwise, it's like comparing a Panzer 3 with its 50mm gun against a late war panther. Both of these were arguably the best tank of their time, but one was built pre war and the other mid war. There were generations of tanks, and the following generation was usually better than what preceded it.
Warships are a bit different, due to both the cost and length of time it took to build. These warships because of these factors also received upgrades, while with tanks with their cheaper costs and production times, you just built new and better ones.
If you look at all warships of WW2, and which were the best from a performance standpoint, the US ships almost always come out best, the biggest reason is because the were built the latest, and most other countries only built a limited amount of ships after the start od the war, at least capitol ships.
You really need to compare warship with other ships of their generation or time. One easy way to break it down would be Ships in service at the start of the European war, and ships in service at the start of the Pacific war, vs. those that were not in service until after the start of the war.
Otherwise, almost every class of ship would have to go to the US, as they built far more 2nd and third genration warhips than any other nation. The only arguable class might be the Battleship, where the Iowa and Yamato are real close, and destroyers, which due to smaller size were made throughout the war by many nations.
Just to break it down for pre and post start of the pacific war, I'd do as follows:
Pre war battleships:
1) Yamato*
2) Bismarck
3) A few here, Nelson Class, Vittorio Veneto Class, North Carolina Class, Prince of Wales Class
* Was comissioned a week after the start of the War
Pre War Carriers
1) Shokaku Class (remarkably durable, the 5" Deck armor helped a lot. This was main deck armor though, not flight deck)
2) Yorktown Class
IMO, the Shokaku was a better carrier, but was limited a bit by carrying 72 planes instead of the 90 of Yorktown. This was due though to the fact that only the Kates of the Japanese planes had folding wings, while the on the US carriers the majority of the planes had folding wings. Hangar space was very similar on the two carriers. This is a real close comparison though, as the Shokaku had better speed but the Yorktown class had better DP weapons, the 5"/38 was probably the best dual purpose weapon of the war.
Oh well, Cruisers and Destroyers later!