I'm personally of two minds on this. There is a delivery surcharge built in most places to cover the cost to deliver the food. However, it's a service that's being provided to get the food to you, whever you may be. I always tip a delivery driver or server, or even the bartender who gets my to go order ready when I pick up lunch at the local pub, but I know people who don't, for various reasons.
For delivery, if the food gets there hot and within a reasonable amount of time I'll do what I do with servers and tip about 20-25%. If the food isn't so hot any longer or it takes longer than promised (excluding reasonable traffic problems), then I cut it down to 15% or so.
Question: did the DELIVERY take 45 minutes itself, or was it 45 minutes from when you called the order in? If it was 45 minutes on the road, that could be a problem and why people didn't tip so well. If the whole order was ready in 45 minutes and it was for a large group, that makes a bit more sense.
In any case, $10 tip for a $25 food bill? Absolutely over the top acceptable. $6 is acceptable. I probably would have given him $30 and told him to call it good, and that would be good enough. That's still 20% of the bill. It sounds like this delivery driver was being unreasonable in what he should be getting tipped. Yes, it's outside their regular delivery radius, but that doesn't automatically mean he gets more money from you.