Fermented sausages, processed through microbial fermentation, have a long history and cultural significance. The fermentation process not only extends shelf life but also enhances flavor, texture, and nutritional value, making them integral to many global food cultures. These products can be classified into two categories based on fermentation methods, microorganisms used, and flavor: Western and Eastern. Western industrially produced sausages (e.g., salami, chorizo, longaniza, and pepperoni) commonly utilize exogenous starter cultures during initial fermentation to ensure product consistency, which create complex flavors like acid, fruity, and smoky. In contrast, Eastern traditional fermented sausages (e.g., Sichuan-style Chinese sausages, Nham, and kimichi sausages) predominantly rely on spontaneous fermentation, with their ingredient formulations and processing techniques profoundly reflecting regional artisanal characteristics. This review explores the production processes, microbial community succession, and their effects on flavor, comparing Western and Eastern fermented sausages in terms of microbial species, fermentation processes, and flavor mechanisms. The findings show that Western products tend to have more concentrated microbial roles and more complex flavors. The characteristic flavor profiles of Eastern fermented sausages primarily derive from region-specific ingredients (e.g., Sichuan pepper, glutinous rice, and kimchi), while their low standardization in production processes results in remarkable regional variations. As globalization advances, the international production and consumption of fermented sausages increase, and optimizing microbial selection and fermentation environments will be crucial to enhancing flavor, nutritional value, and food safety to meet the diverse needs of consumers worldwide.