I'll admit that it would be the height of arrogance to tell one of the world's most successful investors ever which stock he should buy next. Warren Buffett doesn't need any help in picking stocks. But if Buffett were to ask, there's no question in my mind which stock I'd recommend.

It's a stock he knows pretty well. Actually, Buffett has stated in the past that he regretted not buying this stock years ago. And as recently as two years ago, he gave serious thought to buying it.

Which stock is it? The top stock that I think Buffett should buy but hasn't yet is none other than Google parent Alphabet (NASDAQ:GOOG) (NASDAQ:GOOGL).

Search bar in front of hands on laptop keyboard

Image source: Getty Images.

An Applesque stock

At Berkshire Hathaway's (NYSE:BRK-A) (NYSE:BRK-B) shareholder meeting in 2017, Buffett listed several reasons he led Berkshire to load up on Apple (NASDAQ:AAPL) stock. At the top of the list was that Apple is a consumer company rather than a technology company. Buffett has been averse to technology stocks for most of his career primarily because he doesn't understand them.

His primary reason for viewing Apple as a consumer company was its strong brand and its ecosystem of products and services. Both of these give Apple a moat -- a competitive advantage that Buffett likes the companies he owns to have.

I'd argue that Alphabet has those Appleseque qualities. Let's look at its brands. When you think of a search engine, what's the first name that comes to mind? What about video search engine? Browser? Email service? Phone operating system that isn't Apple iOS?

My hunch is that you answered those questions in the same way that I did and most other people would: Google, YouTube, Chrome, Gmail, and Android. There's no question that Alphabet has some exceptionally strong brands.

Alphabet's products also enjoy a really strong moat. This moat stems primarily from what's called the network effect. Products with a network effect increase in value to users as more people use them. That's exactly what has happened with all of Alphabet's core products.   

The Oracle's objection

So why hasn't Buffett bought Alphabet? He said in 2017 that the company has too much technological uncertainty over the long term. Far be it from me to question the Oracle of Omaha. But I'm about to do it anyway in this case.

Granted, several of Alphabet's famous "other bets" have technological uncertainty. The company is pursuing some seemingly wild ideas, including using stratospheric balloons to provide internet connectivity to rural areas, autonomous drone delivery, and even extending the human life span.

However, these initiatives are only a drop in the bucket compared to Alphabet's core technology focus. I don't see any major question marks on the horizon about the company's search technology or its other top revenue-generating products.

And there's one of Alphabet's other bets that seems highly likely to pay off in a huge way. The company's Waymo self-driving-car business is arguably well ahead of all the competition. Investment firm UBS thinks the unit is worth around $75 billion already and could be a tremendous growth driver for Alphabet for years to come. 

Great words of wisdom 

If there's anyone that Buffett listens to about investing, it's his longtime business partner Charlie Munger. Ten years ago, Munger said Google had a "huge moat," adding that he had "probably never seen such a wide moat." That moat is even bigger today than it was then.

Another piece of wisdom that all investors should know came from Buffett himself. He wrote in his 1989 letter to Berkshire shareholders: "It's far better to buy a wonderful company at a fair price than a fair company at a wonderful price."

Alphabet has a great moat and is a wonderful company. The stock isn't cheap, but neither is it too expensive. Actually, Alphabet's trailing-12-month price-to-earnings ratio is less than Berkshire's. 

Buffett might not pick Alphabet as his next stock to buy. However, I think if he doesn't, he's forgoing a great opportunity for big long-term returns.