1905: Russo-Japanese War is an interesting title, but US Navy Plan Orange is the coolest. Now, if I could just find some players or a VASSAL mod! (I would make my own, but I am not familiar with creating mods.)
I'm honestly torn between GREAT WAR AT SEA: MEDITERRANEAN and JUTLAND. Both have scads of scenarios and a huge variety of ships, so both games are quite rich. Sure, I do like the "hypothetical conflict" games like WAR PLAN ORANGE, WAR PLAN BLACK, WAR PLAN RED, and WAR PLAN GOLD, but the World War I games are the best. At least in my book. Of course, the system was designed for them!
I didn't play the original, but the second edition of Ironbottom Sound that Moments in History did is quite good. There's some errata for the ship data sheets, and I don't know if new ones were ever published, but it's still a very good game.