Sustainability in art is crucial for fostering intercultural understanding and preserving cultural heritage, which is essential to promoting the Sustainable Development Goals (SDGs). In previous research on Western and Chinese art, studies typically focused on individual artists and summarized their aesthetic values, often suffering from a lack of comparative analysis, a unidimensional sensory perspective, and a deficiency in comprehensive aesthetic evaluation standards. Consequently, this study selected representative watercolor works from five master artists in Western and Chinese art history as an example, constructing a comprehensive aesthetic evaluation system focusing on composition, color, themes, and techniques. Beginning with the influence of aesthetic and non-aesthetic perspectives by natural experimental method, the research employs correlation analysis and structural equation modeling to analyze the functional relationships between evaluative factors, perspective forces, and the overall aesthetic appeal of the paintings. Furthermore, the study reveals the distinctions between Eastern and Western paintings through multi-group analysis. Key findings include the following: Evaluation factors have varying effects on the influence of aesthetic and non-aesthetic perspectives. All factors, except conceptual expression (X12), brushwork expressiveness (X14), and watercolor language (X16), positively impact the overall aesthetic appeal. In mediation effects, X16 positively mediates between the influence of aesthetic perspectives and the overall aesthetic appeal. Factors such as warm–cool relationship (X8), X12, emotional atmosphere (X11), X14, and X16 positively or negatively affect the relationship between non-aesthetic perspectives and the overall aesthetic appeal. Multi-group analysis reveals significant differences in the evaluation factors and mediation effects that influence the overall aesthetic appeal. This study demonstrates the relationship between evaluation factors from different perspectives and aesthetics, providing valuable insights into evaluating Eastern and Western art. This evaluation system is applicable to academic research and practice in cultural heritage preservation and evaluation and art education, facilitating a deeper understanding of artistic values and promoting cross-cultural exchanges.