Country star Glen Campbell has had his shares of ups and downs in his more than four decades in the music biz, and now the "Rhinestone Cowboy" singer is reflecting both on his hard times and his celebrity pals.

"I really made some bad choices," Glen tells ET, going on to say, "Oh it was bad, it was. Drugs, drinking. Stupid things that you do."

But Glen cleaned up his act, and says of his life now: "Oh, it's wonderful. I look at people now and say, 'Wow, I was in that place one time.'"

What does Glen have to say of his pals in the music industry? "[Frank] Sinatra really was a fun guy," Glen reflects. "He had a great sense of humor."

Glen says Elvis Presley was like a brother to him, saying of the King: "Oh, he was fun. He was definitely fun. He liked to laugh, Elvis liked to laugh. He'd always have that big, crooked smile on his face."

And he says of the Jackson Five, "They just knocked me out. My god they could dance, boy. I tell you. And spin on a dime and stomp. Especially Michael [Jackson]."

Campbell's latest of his dozens of albums, Meet Glen Campbell, is hitting record store shelves on August 19.