Arriving with jet lag, 2 days is just enough to hate Delhi and decide you'll never go back. You need one or two more days. Delhi is one of the world's great cities; it can be a rough and unpleasant city, but there is an awful lot to see.

I occasionally stop in Delhi for 2 days, but I know the city and know what I'm going to do. The metro has made a big difference to the ease of getting around.

There are a couple of neat books by Mayank Austen Soofi and a couple of guided walks of Delhi that would make sense for you to check out, given the 2-day limit. As the others, Delhi is too big to really make sense of in 2 days. A week probably

i think 2-3 days in delhi is good enough....

It's going to be hot, hot, hot. I personally can't think of anything more tiring than covering Delhi's major sights in the summer, and in a rush. But YMMV