It's not like they just made Iron Man 12. They are doing different things. Why hold back on something like Guardians of the Galaxy or a Shield TV show just because Thor 2 is coming out and it's a Marvel comic too.
Marvel is an outstanding source for some great characters and stories. Now if 2/3rds of everything they were doing featured Robert Downey Jr, then it would be overkill, but as long as they are keeping fresh stuff coming, I say roll on. I've liked everything they've done so far.