I'm really happy for Andy. I didn't mind who won either way, but for him to pick himself back up so soon after the Wimbledon final and win a gold medal so convincingly in front of a home crowd is a great achievement. 
Would've been nice for Roger to complete the Golden Slam but he already solidified his position as GOAT and doesn't really need this gold medal to prove it. And he still has a gold medal from Beijing.
I'm happy for Del Potro too - he played such a great match against Roger that it would've been a shame to see him leave without a medal.