Do not make such bold comment of 50 years... It looks little better in the sub cities region which are built around it recently.
Delhi is ahead of Dhaka in some of the following sectors:
1. Much larger land
2. Better public transport system
3. Already made some of the sub cities
4. Better infrastructure.
But I would like to remind you that Dhaka is already working on all of these. Within the next couple of years when all of these projects will be done then Dhaka will look completely different.
But seeing all these township and infra development Bangladesh will work on to keep away all these trouble.
This is the video on New and Old Delhi:
I went there. It is little ahead of Dhaka but not something extraordinary.
This Gurgaon and Noida may look beautiful from outside... but many residents are not happy with the planning and many factors..
N comparing Dhaka with Patna... ... Your home region Banaras is not even in any near comparison with it. Not to mention Bihar (poorest then even sub saharan africa) where you also have some link. Kolkata is only ahead in terms of metro and better transportation system. But once done it will be placed much behind then Dhaka. Already if any one visit the 2 city can see that Kolkata is much dirtier then Dhaka.