We stayed at Citadines Central Shinjuku for one night as part of a road trip around central/northern Honshu and found it to be distinctly average by Tokyo standards but not bad at all.
The location is very good, deep in the heart of Kabukicho (Tokyo's red light district), surrounded by many bars and restaurants and close to an entrance to Shinjuku station which is useful.
The room was on the 5th floor, and very compact (as with most Tokyo hotels), the bed was comfortable and there was a good view of the street out of our window. The wifi was quite slow compared to most hotels these days, the shower was wonderful though!
I'm struggling to find much more to say about it other than it was adequate and served a purpose!