A synonym of “really good” could be “excellent”.
“Really good” implies something of high quality, extremely satisfactory, or outstanding. For example, “That movie was really good. I enjoyed it a lot.”
“Excellent” also conveys a similar meaning. It suggests something that is superb, exceptional, or of the highest quality. For instance, “The service at this restaurant is excellent.” It often implies a degree of superiority and is used to praise or compliment something.
Another synonym could be “terrific”. This word indicates something that is extremely good, wonderful, or impressive. For example, “She did a terrific job on the project.” It has a more enthusiastic and energetic tone compared to “really good”.
“Outstanding” is also a good synonym. It means remarkable, superior, or standing out from others. For example, “His performance was outstanding.” It emphasizes the exceptional nature of something.
In conclusion, words like “excellent”, “terrific”, and “outstanding” can be used as synonyms for “really good” to express a high degree of quality, satisfaction, or admiration.