General:
* Brilliant
* Dazzling
* Exhilarating
* Inspiring
* Impressive
* Radiant
* Sparkling
* Stunning
* Vibrant
* Vivid
Specific to Performance:
* Energetic
* Exciting
* Thrilling
* Powerful
* Dynamic
* Engaging
Specific to Appearance:
* Beautiful
* Gorgeous
* Magnificent
* Splendid
* Striking
The best antonym will depend on the specific context in which "lackluster" is used.