Iams isn't the worst food in the world (probably it's better than Eukanuba) but it isn't especially good either. Both are largely made up of cheap fillers (grains). A good dog food should be mostly meat, with minimal grain content.
There are literally thousands of threads here about kibbles, and how to choose a good one. Just browse through this forum

Some of the most recommended ones include Canidae, Wellness, Innova, Chicken Soup (for the dog lovers soul), Royal Canin and California Natural. There are plenty of other good brands though. Avoid anything with corn, corn meal or beet pulp high on the ingredient list.
In general, try to buy the best kibble you can afford. You usually feed a lot less of it, so it's not as expensive as it may appear

Good nutrition will usually save you in future vet costs too.