"I don't think we're in any sort of bubble like '05, '07, but we're in the middle of a recovery." Gray said, noting Blackstone was likely to put more money to work abroad. "The U.S. has gotten more challenging for us. It's still a good investment environment, but not a great investment environment."
Gray's comments came during an on-stage interview with hedge fund manager Bill Ackman at the Harbor Investment Conference, a charity event in New York City on Wednesday.
(Read more: Blackstone's quarterly earnings more than double; shares rise )
On emerging markets, Gray said the recent economic turmoil represented an opportunity for "attractive investment" given some capital flight.
"In terms of the fundamentals things have slowed, but the bottom hasn't dropped off," Gray said, noting recent profitable purchases of malls in China and Turkey and technology office parks in India.
On Europe, Gray said the real estate marketing was "bottoming" and predicted slow growth. Ireland, the U.K., Italy and Spain have either reached their bottom or begun to rebound, he said.
(Read more: Blackstone-controlled Brixmor's shares rise 4 pct in debut)
Ackman also asked Gray what are the largest macroeconomic "black swan" risks.
Gray had two warnings. First was the U.S. not getting its "fiscal house in order" and being hurt in the long term by growing debt. Second was the global threat of increasing income inequality.
"What I worry about is that governments in their reaction to try to remedy this could do some things that end up harming growth in a significant way," Gray said without elaborating on those potential policy changes. "But I understand fully why people are trying to address this--because it's a real challenge."
Gray, 44, is the top candidate to succeed Hamilton "Tony" James as Blackstone's second in command, according to a recent report in The Wall Street Journal.
Gray said Wednesday, however, that the Blackstone's leadership was not "changing for the foreseeable future."