Re: Howard says that not getting to Reprise his Ironman role killed his career!
Let's not get carried away here. Howard was 10x more popular than RDJ (and remains more popular than Patrow, Bridges and Favreau) with the general audience at the time. That's why Marvel paid him what he demanded. Now that RDJ is an A-List celebrity again however, Marvel kicked his ass to the curb (something that Marvel Studios isn't afraid to do with big name actors -- which has earned them a reputation). Justice was done. Howard was asking for too much and he's apparently complicated to work with (similar to Jamie Foxx).
Cheadle is a great actor but his chemistry with RDJ was off. Marvel did the right thing but Don wasn't as well-received as Howard. At this point, casual fans have accepted that Terrance has been replaced but Cheadle won't be as charismatic as Howard in alot of people's eyes.