素敵（すてき） means wonderful, lovely, or great, especially when something fits your personal taste or feels emotionally appealing.
Use it for compliments about clothes, interiors, atmosphere, gifts, or someone’s personality. It often sounds softer and more refined than すごい.
Compared with 素晴らしい（すばらしい）, which can praise something as objectively excellent, 素敵 is more about your personal impression: “I like this, and it feels special.”
It is used by everyone, but it can sound slightly elegant or gentle. In very casual male speech, すごい or かっこいい may feel more natural depending on the situation.