Depends u know....
Pirates of grill or The GT Road (barbeque style dinning) they have variety in main course too.
Diggin, Sky High, Terminal 21, The Lodhi Restraunt (it's in Lodhi Garden) here can have nice view, and good photo backgrounds. different experience as they aren't closed wall Restraunt.
Barbeque Nation, Pirates of The Grill, Punjab Grill and AB's Barbeque are some great options since they have buffets and will save you from the hassel of choosing fishes on Ala-carte basis.
Indian Accent at The Lodhi is a truly special place to celebrate your Anniversary
If budget isn't a concern, then you can go for Sevilla at The Claridges, Ottimo at Westview at ITC Maurya, Thai High in Mehrauli
Choose restaurant and bar in rajouri garden. Here you will find DJ, good ambience, unlimited buffet, drinks and non veg also.