I feel like I want to mock my friend because he's excited about receiving a gift from his long-term employer.
Why would you mark your friend about receiving a gift from his employer?
I want to make him feel bad about himself
It can be fun to tease our friends sometimes, but it's not good to undervalue their accomplishments. Making your friend feel dumb is quite mean, and if you do that they are likely to reevaluate their friendship with you. Instead of making fun of your friend, try to be supportive and congratulate them.
It's alright, it's only a gift.
Only a gift for you but it's something special for him. It's a rare occurrence for a company to give gift to employees for being a great worker. Let him have the limelight.