This study investigates the paradigm shift in the game industry driven by game-type UGC platforms that are building creator-centric ecosystems. Recognizing the limitations of existing theories in explaining these platforms' operational mechanisms, this research aims to identify the core systems constituting the creator support ecosystem and analyze their organic interactions. Through literature review, five core systems were conceptualized, followed by comparative case analysis of Roblox and Fortnite. The findings confirm that game-type UGC platforms' creator support ecosystems comprise five essential systems: (1) Creation Tools System, (2) Interaction System, (3) Sharing & Discovery System, (4) Value Distribution System, and (5) Governance System. Furthermore, these systems do not operate independently but are organically interconnected, forming a virtuous cycle of creation → collaboration/improvement → diffusion → reward → motivation. Based on these findings, a 'Creator Support Ecosystem Model' is proposed. This study provides a new analytical framework that systematizes UGC-related concepts into five core systems, offering both theoretical foundations for future research and practical design guidelines for building successful UGC platforms. The proposed model enables strategic understanding of how these elements organically constitute a complete ecosystem.