No. He didn't come to the NBA soon enough to be considered on the all-time list. He belongs at the top of the "What if he came to the NBA sooner?" list. If he came to the NBA in his early to mid 20s I think he would have challenged Olajuwon for best ever.
But still, Mutombo is better than Sabonis no question. Probably better than Schrempf and Smits. Mutobmbo has played 10 years. Sabonis has only played 6 years, and has pretty much retired from the NBA.