Service catalog and maturity
Winner: AWSAWS still has the widest catalog — there is virtually no service category where AWS does not have a production-grade managed offering. For most general workloads, AWS is the lowest-risk choice precisely because it has been running them at scale longest.
Azure has caught up dramatically. Its catalog is comparable in breadth, with Microsoft-stack integrations (Active Directory, Office 365, Power BI, Dynamics) that no one else can match.
Google Cloud is narrower but extremely deep in its specialisms — Kubernetes (GKE is the reference implementation), BigQuery, Spanner, Pub/Sub and AI/ML platforms. For workloads in those categories, GCP often beats both competitors on developer experience.