It's been quite a year for the tech sector. Compared to growth of the Standard & Poor's (S&P) 500 index (SNPINDEX:^GSPCin 2015, tech stocks left the industry benchmark in the dust. As a result, focusing on just a few of the high-flyers from this past year is sure to omit many worthy of inclusion. But alas, not every top-performing tech stock can make the list.

Three industry stalwarts in particular should make any list of the best tech stocks of 2015, albeit for different reasons. Both Netflix (NASDAQ:NFLX) and Amazon.com (NASDAQ:AMZN) shareholders enjoyed triple-digit growth in 2015, but their respective business models aren't for everyone. Facebook (NASDAQ:FB) can't boast the same stock price appreciation, but it took significant strides this past year and is ideally positioned for future growth.

Over the top?
There was a bit of a stock price hiccup when Netflix announced Q3 earnings on Oct. 14. Though total memberships, revenue, and net income all increased year over year, some investors weren't enamored with the domestic growth of Netflix domestic memberships. The share price blip was short-lived, however, and Netflix stock has since more than recovered: It's up 140% in 2015.

Netflix investors aren't overly concerned that its earnings per share (EPS) of just $0.07 last quarter was half the year-ago period's, buying into CEO Reed Hasting's objective of focusing on member growth, content, and building out infrastructure, with the notion that EPS will come. And Hastings may be right, considering the growing trend of cord-cutters opting for over-the-top (OTT) alternatives like Netflix over costly cable or satellite providers.

All hail the king
Amazon.com foray into the video streaming space with its Prime service isn't the only thing the company shares with Netflix; it has also decided to forego profits to some extent as it builds out its array of warehouses, develops cutting-edge delivery drones, and boosts its top line -- as it did yet again last quarter. Amazon.com shareholders also enjoyed a stellar 2015 as its stock more than doubled.

With CEO Jeff Bezos' emphasis on revenue growth in lieu of bottom-line results, Amazon.com is trading at 120 times next year's earnings. That's actually cheap compared to Netflix and its trading multiple of a whopping 450 times future earnings, but again, investors don't seem to mind. Perhaps shareholders are right in not concerning themselves with bottom-line growth as Amazon.com continues to spend.

The proliferation of mobile devices as digital shopping tools combined with consumer's growing comfort in buying online should push Amazon.com to even greater heights going forward. To put its online shopping dominance into perspective, Amazon.com accounted for an estimated 36% of this year's Black Friday online shopping bonanza.

Now for something completely different
It could be argued that Facebook, with its "meager" 36% jump in share price this year, doesn't warrant a spot on a list of the best tech stocks. After all, compared to the triple-digit returns both Netflix and Amazon.com shareholders saw in 2015, Facebook's performance looks a bit anemic. However, Facebook did a lot more in the past year than reward investors with its solid stock price performance: It paved the way for another year of big-time growth.

This past year saw Facebook finally take its video ad alternatives out of the testing phase and into mainstream production. Though COO Sheryl Sandberg wasn't forthcoming on specifics, she did say that video remains a priority and is already beginning to pay dividends. Investors can now add Facebook's wildly popular Instagram into the revenue-generating mix, too. Combined with video ads, some pundits suggest the photo-sharing site could be worth as much as $35 billion in its own right.

Facebook is nearly ready to introduce its virtual reality (VR) Oculus Rift headset to the gaming masses "early in 2016." Like Instagram, VR offers a world of opportunity in the coming years, as some estimate the total market value could grow to $30 billion by 2020. Finally, there's WhatsApp's nearly 1 billion monthly average users (MAUs), Messenger's 700 million, and Facebook's bevy of 40 million small business owners just waiting to be monetized.

The triple-digit returns of Netflix and Amazon.com this past year, along with Facebook setting the table for years of solid growth, move them to the top of the best tech stocks in 2015 list.

Tim Brugger has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Amazon.com, Facebook, and Netflix. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.