Delhi, being capital of India has a vivid heritage. People from all the states of India reside in Delhi and thus it has turned out to be a melting pot of all the sub-cultures in India. Naturally these people bring their respective cuisines with them. Therefore it will not be considered exaggeration if we say that Delhi is a Mini India in itself. So if you visit Delhi, try as many distinct cuisines as you can to get the feel of vivid Indian delicacies.
Start with Old Delhi or Walled city area popularly called 'Purani Dilli'. Here you will find a platter of vivid cuisines starting from Tandoori items and Kabobs at Karim's to authentic Mughal sweetmeats at Ghantewala Sweet. Each alley in Purani Dilli has its own range of cuisines. If you go to Ballimaran, you have Nehari at Bismillah and authentic Afghani Pilao and Green tea at Pathanwadi. Gali Paranthe wali will attract you with the aroma of Pure Indian un-synthesized fat popularly called Ghee. The paranthas are very tasty and have ingredients that have remained unchanged since the times of Great Mughal. Want something spicier: head for Chaat Corner near Chandini Chowk Metro Station. If you plan to call the day, water down these with a cool grass of Rabri Faludas at Giani near Fatehpuri Masjid. These are some of the authentic cuisines of Delhi. The major South-Indian delicacy is Dossa-Sambhar. Apart from it, you can also try Idli-wada and Rasam. Western India is represented by Marathi and Gujrati cuisines, major one being Bada Paw, Paw-Bhaji and Dhokala. Eastern India is not behind and there are lots of authentic Bangla Cuisines apart from Assamese and Bihari foods. Macher Jhol, Jhinga, Kachalu and Macher-bhat are the major delicacies. No discussion on cuisines can be rounded off without mentioning Bangla Sweets such as Rossogulla, Sondesh, Dooth-puli, Cham-cham and Lavag-lotika. Last but not the least is the cuisines from Oudh. Biryanis, Kabobs, Nehari, Nalla are some of the very popular non-vegetarian dishes from Oudh where as Tehri and Pilao represent vegetarian cuisines.
You can also go for Continental, European and other Asian cuisines if you like. There are some of the very popular fast-food giants such as Subway and Mc. Donald's, who have their outlets in Delhi.