Everybody has been cheering the great news that the stock market has performed brilliantly so far this year -- the best quarterly gain that the S&P 500 and Dow have clocked in 14 years, to be precise, and the Nasdaq's best in over 20 years. The market is on a roll, and has shattered even the most cheery analysts' predictions. And what is responsible for all this financial good fortune? Why, Apple (Nasdaq: AAPL), of course.

Well, OK, not entirely. But Barclays contends that Cupertino has contributed 15% to the S&P's rise just by itself, and that's nothing to sneeze at. The company's nearly 50% rise in stock value in the first quarter is pretty astounding, and the 72% increase from a year ago prompted analysts to opine that the stock had carried the S&P for most of the year. Here's the kicker, though: Apple wasn't the No. 1 performer. Sears Holdings (Nasdaq: SHLD) holds that honor, followed by Bank of America (NYSE: BAC), then Netflix (Nasdaq: NFLX).

For those following the soap opera that has become Sears' claim to fame, the nearly 110% increase in the company's stock over the past three months probably confounds. Each time bad news breaks, whether it is additional store closings or yet another top executive bugging out, the stock enjoys a rally. Inexplicable, I know; the only thing that seems reasonable is that investors think there will be a big payoff when owner Eddie Lampert takes the company private. Meanwhile, the roller-coaster ride continues.

Bank of America's 72% stock rise over the past three months still has the company's shares trading shy of $10 (and still well under book value), so there wasn't a lot of value accumulated during that time. Between the bank's exposure to the foreclosure market, the robo-signing debacle and losing customers over the $5-per-month debit card fee that never was -- well, let's just say it's been a tough year.

Netflix, of course, suffered a precipitous drop in its share value after the Qwikster incident -- a customer relations gaffe from which it still has not recovered. Even though the change never took place, investors are obviously still wary. Now, there is some evidence that there may be a Qwikster redux on the horizon, so the 66% value increase experienced during the past quarter may vaporize soon.

Percentages don't always tell the whole story
Of course, Apple's rise was steadfast, building on its business savvy and great, desirable products -- and not from sinking so low that even minor gains became magnified in importance. If I had lots of money and wanted a sure bet, I'd probably pick Apple as an investment vehicle -- though I might consider Netflix, as well, but not until this weird Qwikster-redo is sorted out.

While it was very sporting of Sears, B of A and Neflix to help the S&P reach its recent lofty heights, it is always important to remember that sometimes, the numbers don't tell the whole story. Astounding gains over a short period of time may mean a true turnaround for a company, but just as often, they don't. Keep in mind that due diligence in investing is just as important when the market is soaring as when it is snoring. And, yes, I did just make that up.

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