Which AWS service is primarily focused on creating high-quality datasets for training machine learning models?

The service that is primarily focused on creating high-quality datasets for training machine learning models is Amazon SageMaker Ground Truth. This service facilitates the process of data labeling, which is essential for supervised machine learning. Ground Truth offers built-in workflows for data labeling, including human annotation, and automates parts of the labeling process with machine learning to reduce costs and improve efficiency.

By enabling users to create diverse and accurately annotated datasets, SageMaker Ground Truth enhances the model training process, ensuring that machine learning models learn from high-quality, relevant data. This focus on dataset quality is crucial for developing effective machine learning solutions.

Options like Amazon S3 serve as a storage service for datasets but do not inherently assist in dataset creation or labeling. Amazon QuickSight is primarily a business analytics service, and Amazon Polly is a text-to-speech service. Thus, they do not fulfill the primary function of dataset creation for machine learning purposes.