For me its a tough call between the Excelsior and the Galaxy. Both ships bore the name enterprise and both were ahead of their time in terms of design and engineering. While the Galaxy Class in-universe must have a fantastic reputation after the adventures of Picard and Co, the legacy of the Excelsior Class is a little more mysterious or at least under-represented in modern Star Trek. They were kept in service for at least ninety years by the end of the dominion war but not much is known about the exploits of the Enterprise B or the Excelsior post St VI: TUC. Speaking purely from a design perspective, I lean towards the Excelsior Class as the Galaxy seems ungainly and looks a little cumbersome IMO, despite its cutting edge technology. The Exc is large, streamlined and unmistakably federation. Its well-balanced, its proportions are great even if the entire ship looks a little stretched out length-wise. Now I have no idea how the impulse drives move the ships in zero gravity/vacuum but the Exc Refit was obviously capable of maneuvering itself with ease with the extra engines at the rear of the saucer. If it wasn't then this change seems entirely redundant! The new nacelle caps are a welcome addition to the plain black strip of the original, although I wish they made the bussards red instead of blue! Regardless of those couple of nit-picks, the Excelsior just about takes the top spot over the Galaxy as in my opinion its performance and reliability are the natural reason for it to have stuck around for so long. Now with the advent of ST PIC, there are many more designs to choose from, many of them based on the venerable Galaxy Class. So after these two, my third place would have to go to the Ross Class. It reminds me of the fan Charlestown Class and I love the Sovereign style hull triangle on the saucer!