i liek piano

this question doesn't make sense

A musical instrument has 2 primary purposes - to lead a piece (usually as a substitute for the human voice), or to provide accompaniment

The best lead instrument would be one with the greatest range of possible expression, while standing out from the accompaniment in terms of pitch and tone. The range and versatility of an electric guitar and synthesizers - particularly their ability to output bright, ear-catching sounds - makes them some of the greatest lead instruments ヽ(´ー｀)ノ

In terms of accompaniment, the best instrument would be one that enhances the lead vocal/instrument the most without conflicting or getting in the way of the lead. The four primary components of music are melody, harmony, bass, and rhythm - since the lead vocal/instrument is typically providing the melody, the best accompanying instrument would be able to offer all 3 of the remaining components by itself, even standing in for the lead to provide the melody at times. That makes instruments like piano, organ, guitar, and polyphonic synthesizers some of the best accompanying instruments ヽ(´ー｀)ノ

piano is such key compoment to so much music, and sounds lovely just by itself too. I play the saxophone tho.

>piano is such key compoment
Surprise pun!

There isn't a "most valuable" or "important" instrument in music, it highly depends on what kind of sound you're looking for. You can do an innumerable amount of things with a piano, but it'll never sound like a trumpet. A good composer knows exactly what specific instruments to use for a specific section, and mostly importantly knows how to "blend" the instruments together so that they all contribute to the song.

That being said, I think what >>4420 said is a good answer to your question. There's a reason why Bass, Drums and Guitar/Keys are a must for pretty much any band. Drums give rhythm, Bass gives bass, Guitar/Keys do the rest (accompaniment, melody, harmony)