Speculation linking Rooney with a move to the Chinese Super League has intensified amid reports his agent Paul Stretford has travelled to the country to discuss a possible deal.
The transfer window in China does not close until the end of February.
West Ham boss Bilic, who has coached against Rooney in the Premier League and at international level from his time in charge of Croatia, thinks the striker still has a lot to offer.
"He is 31, he definitely has the quality to stay in Europe and he will have enough choices," Bilic told reporters ahead of West Ham's away game against Watford.
"On the other hand he has done everything, he has nothing to prove and it is difficult for players like that - who have done everything - to find new challenges.
"You captained Manchester United and have been one of the best players in Europe for so long, so where can you go? Of course it is his decision."
Bilic thinks that whatever Rooney opts to do, his legacy in England is secure.
"He is, for me, a proper Premier League legend along with Steven Gerrard, Frank Lampard and Thierry Henry," added Bilic.
Rooney is hoping to recover from a muscle problem to play in Sunday's EFL Cup final against Southampton at Wembley, a match that offers him - should a China switch come to sudden fruition - the chance to win a farewell trophy.