LMSys Chatbot Arena is a crowd-sourced ranking with an ELO system: basically users a presented with 2 hidden models, they get the answers of the 2 models when presenting their request, and they vote which one performed bests, which realized one marche and updates the ELO scores. This is the closest thing that we have to a gold truth for LLM evaluation: and Gemma2-27B performs extremely well in Chatbot Arena ELO.