Hi! So glad you had a wonderful experience for your first cruise!
We have about 60 cruises under our belt, on several different cruise lines, and, truthfully, we have never had a bad cruise or met a ship that we disliked.
Celebrity has a great product, and you would not go wrong sticking with them. Their loyalty program is one of the best. Just be careful if you want a traditional balcony as the newer Celebrity ships have an infinite verandah which is basically inside the cabin with a big window that opens.
On the other hand, you might enjoy trying some of the other cruise lines for variety of itineraries, dining, and entertainment.
If you enjoy daily lectures and enrichment programs, Crystal is noted for those.
If you bring children or grandchildren, Royal Caribbean is a must! The newer ships are amusement parks with propellers!
Good luck with whatever you choose!