Don,
I think Patak's is the main global brand for Indian sauces and pastes.
But really, drop the Patak's and move slowly to the spice aisle at the Indian grocery. Other than a helper for Tikka marinade, don't use it.
Grab the following: cumin, coriander, garam masala (unless you make your own!), turmeric, hot chilli powder, fenugreek leaves (methi), paprika, madras curry powder, cloves, cassia, and bay leaves. Those are probably the basics, but others will be needed depending on your curry tastes. Probably cost you less than a large jar of Pataks!
Make a base gravy (Bruce Edwards, Saffron, and SnS are personal favourites of mine)
Then make a curry - if Tikka Masala is your thing try Curry King's - you can't go wrong. For the Chicken Tikka, try Blade1212's recipe.
The base gravy + curry method might seems tedious and time consuming at first, but the base lasts for many a curry. The Patak's stuff is really only eliminating the base gravy creation stage, and the results are FAR inferior in general.
Saying that you see a lot of Indian people buying it is similar to saying I see a lot of Italians buying Chef Boy-ar-dee Pasta meals.
--- Josh