If we are talking true dark skies and at least a 10-12" scope, then yes in our southern skies M83 is about the best, NGC 1365 is also pretty good, then although not quite as obvious, NGC 1566 shows some spiralness too as does NGC1300 in a big scope. In the northern sky however, visually, M51 leaves all spiral galaxies in its wake, where under a dark sky, it's face on spiral structure is thick and dense and plain to see, down to a 6" or 8" scope and in scopes in the 18"-20" realm or larger, it is positively B&W photographic in appearance. I was fortunate enough to view it in several different scopes, up to 32" at the 2018 Texas Star Party and it blew my mind, so good
Mike