No. Cuba Gooding Jr. didn't appear in the first installment of Iron Man.
You've probably mistaken Terrence Howard's character (Rhodey) being Cuba Gooding Jr. as Howard, at first glance, totally looks like Gooding.
And it appears that there has been a lot out there who thought of the same thing - they had to watch the movie several more times to realize that it was actually Terrence Howard and not Cuba Gooding Jr.
See Iron Man (2008) Full Cast & Crew, courtesy of IMDb.com.
Of interest, take a look at the 25 Most Unbelievable Celebrity Lookalikes Ever, shared by Cosmopolitan.
Check out Acting Secrets from a Pro, featured at ActorTips.com.