Best is a subjective term, and one that should not be used indiscriminately. It’s all in the context. “That’s the best lasagne I’ve ever tasted,” states that, in the speaker’s experience, that lasagne is the best. No problem. Had the speaker instead said, “That’s the best lasagne ever,” the statement rather casts aspersions on all the other lasagnes out there that may, in fact, be just as good or better but have not been sampled by the speaker within the parameters of her experience.
You can unequivocally make the “best” choice for yourself. You can aspire to be the “best” you can be. You can make the “best” lasagne you’ve ever made. Those are all very good and appropriate uses of the word. On the other hand, you may want to beware of declaring a store, a restaurant, a service, a class, a program, an artist or yourself the “best”, because all the other stores, restaurants, services, classes, programs and artists are diminished to second best or worse by that statement. It may seem like a minor and absurdly literal thing, and it is exactly that, but I assure you that those who have been relegated to second best by your statement will likely resent it and wish that you’d said what you had to say with a little more discretion. The end result is that your supportive statement of goodwill ends up totally pissing somebody off. Or possibly, many somebodies.
It’s an easy fix. Try describing your subject as “one of the best”, or forget the word “best” and go with some other positive adjective like great, wonderful, excellent, first-class...... the list is endless. Really, it’s the best thing to do.