"Bull markets climb the wall of worry...And that's why I think this bull has room to run"

"Remember, bull markets climb the wall of worry. You know, what's going on in the Mideast, Ukraine—those are the worries. Bull markets top off when no one sees a problem on the horizon, everyone is in, there's no one else to come in," he said. "We are not at that area, and we know the public is still very gingerly putting their toes in this market with disbelief. That does not mark a top of the market. And that's why I think this bull has room to run."

Siegel didn't see the Federal Reserve's expected reduction of asset purchases as much of a headwind, either.

"So, if the Fed eases in March or April instead of late in the summer (of 2015), so it goes to 50 basis points, is that going to end the bull market? I mean, that is still unbelievably low compared to anything historical," he said. "So, the 10-year goes from 2½ to 3—and maybe even 3½—that's still extraordinarily low from any historical (perspective). And that's why, again, stocks have that wind of the interest rates going with them no matter when the Fed starts tightening."

 Jeremy Siegel uber-bullish Wharton professor of finance said that the index, which hit an all-time high on Tuesday, has further to climb.

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Chris Hyzy said "We're 5 years into a 20-year bull stock market"

As the S&P 500 topped 2,000 for the first time Monday, Chris Hyzy said that the stock market is just five years into a 20-year bull market.

"I know it sounds easy to say," U.S. Trust's chief investment officer said on CNBC's "Halftime Report." "When you really think about this, this is an elongated business cycle. You're going to have fair value through most of it. You're not going to get a lot of overvaluation."

Read More Why S&P 2,000 milestone has Art Cashin unimpressed
Hyzy identified what he saw as key for the continued bull market.

"You're going to have some very big opportunities inter-sector and themes. M&A is running wild. But the key to all of this is the manufacturing in the next decade," he said. "It's already happening. You've got energy independence on its way. The private sector's piercing through whatever restrictions are being put out there, and you've got technological advancement that we haven't seen since the early 1990s.

"That sets us up for an elongated business cycle, which is about five years into a pretty long secular market."

Hyzy, who expects GDP growth of 3 percent to 3.25 percent for the United States this year, said that he liked the financial sector best of all, with selected technology and oil-service plays.

Read MoreMarket bear becomes biggest bull on Wall Street

Europe, he added, resembled Japan at the outset of its 20-year deflationary spiral. With credit growth contracting, weakness in Germany and French bond yields below that of the U.S., European Central Bank President Mario Draghi "has to act at some point, and it's a little too late."

"I would argue that the first movement on QE in Europe is a good thing for low-quality assets," Hyzy said. "You'll get the big rally. And then you'll levitate for a while if growth doesn't get there."

—By CNBC's Bruno J. Navarro.

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