2023 has turned out to be great for growth stocks so far. The Vanguard Growth ETF (VUG -0.04%) is up 27% year to date. Many individual stocks are trading up even more. But just because stocks have already rallied a healthy amount so far doesn't mean that it's too late to buy growth stocks. Indeed, many of these stocks remain well off their all-time highs.

Let's look at two growth stocks that still trading down about 71% and 32%, respectively, from their relatively recent all-time highs: Roblox (RBLX -2.28%) and Amazon (AMZN 2.48%). Both stocks have real potential to be screaming buys over the next 12-18 months.

Stock chart showing a rising value.

Image source: Getty Images.

1. Roblox

Roblox operates an online metaverse-style gaming platform. Investors looking for a growth stock with great long-term potential should take a closer look at Roblox, which trades down about 71% from its all-time high set in the latter half of 2021.

The company makes a significant portion of its revenue through the sale of an in-game currency called Robux. In turn, users spend their Robux to play games created in-house and by individual users (which Roblox shares revenue with), buy items for their avatars, and enhanced the powers of their avatars to help them complete challenges.

In its most recent quarter (the three months ending on March 31), revenue soared 24% year over year; average daily active users (DAUs) jumped 22%. Hours engaged climbed 23% year over year, and bookings (sales of in-game currency yet to be booked as revenue) rose 23%.

Even with that strong growth, Roblox shares still trade at a reasonable valuation. The price-to-sales (P/S) ratio is 9.9, well below its lifetime average of 18.2. Investors looking to add some growth to their portfolio should consider it.

2. Amazon

Amazon, whose stock trades about 32% off its all-time high, is already a giant with a market cap exceeding $1 trillion and it's expected to grow even larger. Analysts forecast the company will surpass $600 billion in annual revenue by 2024 on the back of 9% to 12% revenue growth this year and next.

Those growth projections account for the potential of a recession this year. A more robust economy could send revenue even higher, since Amazon's core business is somewhat tied to macroeconomic conditions.

Cost-cutting initiatives enacted in response to slowing growth tied to a pandemic-affected economy should help Amazon grow earnings per share (EPS). The company has cut its workforce by over 27,000 and delayed the construction of some large Amazon projects, including the second headquarters in Arlington, Virginia. That belt-tightening is expected to pay off. Wall Street expects Amazon's EPS to rise to $2.58 by 2024, returning the company to levels not seen since the pandemic-induced blowout year of 2021.

The company also has several opportunities to grow into new, exciting areas. Artificial intelligence (AI) is the hot trend on Wall Street at the moment, and Amazon is actively involved in it. For instance, the company has over 500 million Alexa-enabled smart devices in operation around the world. That vast network of AI machines will provide it with useful data to help it further hone its business models.

There are also rumors Amazon is looking into offering a wireless phone and data service bundle tied to its Prime membership. And it expects to use AI to further refine its logistics network, making it even better at delivering products with speed.

Shares remain cheap by historical standards. Amazon trades with a P/S ratio of 2.4, compared to its five-year average of 3.6. That offers an opportunity for investors looking to add shares of this tech mega-cap.