There are quite a few places in Tokyo to see great night views, the Tokyo Tocho Tenboshitsu (都庁の展望室) is definitely one of them, best of all, it’s FREE!
North observation room: 9:30~22:00
South observation room: 9:30~17:30
North observation room: every 2nd and 4th Monday
South observation room: every 1st and 3rd Tuesday
Entrance fee: Free
Here are some of the night view photos I took from the building, the place is basically a room surrounded by glass windows, it was quite hard to avoid light reflection of the windows when taking pictures.
The view should also look quite nice during daytime, although as a personally preference, I fancy city night view more.