This happened to me in the best game it can happen in. Team Fortress 2. It takes a few hours to even understand how all the classes work, and I'd been playing for two years, against people who were on their maiden voyage.
It was ridiculous. My opponents kept getting lost in the payload maps, engineers didn't know how to build, spies didn't know how to disguise, medics couldn't heal, and soldiers kept killing themselves with rocket jumps.
I figured the best thing to say, after killing them all in one sticky explosion, was just "I've played since launch." It pretty much summed it up, no amount of gloating would compare. It's like showing your 100 meter dash olympic gold medal to the neighbor's kid, who wants to race you to the shop.