Unfortunately, I've only sailed on one line in this group: Cunard. We ate in the Princess Grill which was wonderful. They could do no wrong. We ate a couple of times in their "Lido" (can't remember what they called it). They could do no right! It didn't take us long to figure out where we'd have our meals!
I recently went on Silversea, and while I was one of the few people who was not overwhelmed with the cuisine, I hguess maybe my expectations were just very high at the time. i found most of the food to be bland tasting with far too much reliance on creamy sauces rather spices and high temperature cooking.
A steak, foe example, would come out a bland grey color with just a dab of sauce next to it, and perhaps a slice of bacon around it.
I would rather have the Ruth Chris sizzling hot steak, carbonized on the outside and melt like butter on the inside.
The lobster was drowned in mushroom gravy 0 just the world's worst sin for me, as lobster is a very delicate flavor and I detest mushroom gravy.
I have not been on Regent or Crystal recently, unfortunately, so I cannot say. I do remember finding some of the Crystal Food, especially the Japanese, exquisite, but some of the steak we were served was unacceptably gristly in even the most basic steakhouse.
Regent, I recall having uniformly excellent food, and I will say the same for Seabourn, that was so long ago it is hard to remember.
Never been a food snob, but if its good to eat and presented well, what else can you ask for from a floating hotel and bulk (even at that price feeding), unless we fall into the trap of "extras", ie for $20-£100 more per person, and you are now presented with what we deem as a presentable meal in our "specialist" restaurant compared to ordinary dining.