I've been fishing on this lake for 25+ years, and I've seen a lot of fish, so my opinion might be skewed. Fun topic though, because everyone has their own definition of "trophy." I know mine is on the smaller side of the scale when it comes to whitetails.
Salmon - For lake fish I have one on the wall that was 32lbs. Next one will have to be 35+lbs. If I were to mount a Fall run fish it would have to be 35+lbs.
Steel - For lake fish I have one just over 17lbs on the wall, so the next one needs to be larger than that. I want a 15+lb stream fish for my wall badly.
Brown - We screwed up here and tossed back one around 17/18lbs last Spring, and had a customer eat a 17lb fish last Spring. Basically, the next Lake run and Stream run Brown over 15lbs is going on the wall.
Lake Trout - Another screw up last season. We caught a 24lb Laker in the Sandy Creek Shootout. No ice on board, and it was an all white ghost by weigh in skewed my view on getting a mount of this done. So, the next Laker over 21 or 22 pounds will get a seat on my wall.
I have a 6.5lb Largemouth on the wall from Conesus, but I could never get a Smallie from Erie over 5.7, so a 6+lb Smallie is also on the hit list. I'm still waiting for my 40" Pike through the ice.