MSC is another *slightly* controversial cruise line. They are pretty nice though considering that they are more prominent in their cargo fleet. My parents went on the MSC Maraviglia and had a pretty nice experience.
Norwegian is pretty nice. My parents have been on Norwegian once or twice. Great experiences both times. They have some pretty cool ships too, with racetracks on them.
Carnival is a bit controversial. Some people don't like it, some love it. I think it's fine, but they wouldn't be my first choice. There have been many incidents when they get stuck at sea, or there are passenger emergencies. Even my teacher's carnival ship was stuck at sea.
I love Royal Caribbean I have been on the Anthem of The Seas, and it was wonderful. The technology was so advanced and the staff, food, activities, destinations were amazing. Except Nassau. I was tired, and not strong enough to walk around Nassau all day. It was still fun though.
Hello My name is Gabriel Hillman I am obsessed with cruises. But they're extremely expensive and I have only been on one. Either way, I still love them.