General relativity and quantum mechanics provide highly successful descriptions of nature at macroscopic and microscopic scales, respectively, but their conventional formulations are difficult to reconcile in places where strong gravitational fields and quantum effects become simultaneous. This incompatibility between such important theories motivates the development of a consistent theory of quantum gravity. The paper presents a comparative review of the physical motivation for quantum gravity and further examines four major theoretical approaches: string theory, loop quantum gravity, causal dynamic triangulations, and emergent gravity. This review discusses the treatment of spacetime, gravity, and quantum effects within each framework, along with their principal theoretical advantages and unresolved limitations. Particular attention is given to black holes, spacetime singularities, and the black hole information paradox, and the difficulty of obtaining experimental constraints at the Planck scale. The comparison demonstrates that, despite substantial theoretical progress, no existing approach has yet received decisive experimental confirmation. Future advances in gravitational-wave observations, cosmology, high-energy physics, and quantum information-based methods may provide constraints on competing models and improve our understanding of the quantum structure of spacetime