Robert John Downey Junior as Anthony Edward Stark, because seriously he was perfect for the role.
Thomas Stanley Holland as Peter Benjamin Parker. I think his version fits the best. Sorry Toby and Andrew.
Christopher Robert Evans as Steven Grant Rogers.
Scarlett Ingrid Johansson as Natalia Alianovna Romanova, because lets face it, she is the perfect black widow.
Christopher Hemsworth as Thor Odinson.
Mark Alan Ruffalo as Robert Bruce Banner.
Sebastian Stan as James Buchanan Barnes.
Jeremy Lee Renner as Clinton Francis Barton.
Elizabeth Chase Olsen as Wanda Maximoff.
Paul Bettany as Vision.
All other cast members as themselves, I just really like making these.