Apple’s AAPL iPhone was the fastest-growing smartphone of 2008, despite end-of-year sales that failed to maintain the blistering pace set in July with the launch of the iPhone 3G, Gartner researchers reported Wednesday.

“Apple’s initial sell-through dropped significantly as sales fell during the fourth quarter,” Gartner said. “Nevertheless, Apple maintained its third position in the global rankings.”

Nokia NOK still dominates the worldwide smartphone market with a 43.7% share, but overall it was not a good year for the world’s No. 1 manufacturer of mobile phones. Its smartphone sales were flat compared with 2007 and actually fell 16.8% year to year in the third quarter.

Research in Motion RIMM , HTC and Samsung all grew their smartphone market share last year, but none as fast as Apple, whose sales increased 245%. See Gartner’s table 2 below:

New products offering “compelling device experiences and touch interfaces” drove smartphone sales in 2008, according to Gartner research director Roberta Cozza — especially in calendar Q4. With no new iPhone to show in the December quarter, Apple’s sales to end users fell 13.6%, to 4.08 million in Q4 from 4.72 million in Q3, as Gartner counts them. (Apple reported sales of 4.36 million iPhones and 6.89 million, respectively, in those quarters, but roughly 2 million iPhones built in Q3 ended up in inventory, according to Gartner, and therefore didn’t count as sales to end-users.) Still, Apple’s fourth quarter iPhone sales were up more than 111% year to year.

With two new BlackBerry models introduced in Q4, RIM’s sales were up both year to year (84.9%) and quarter to quarter (28.3%). Samsung had a particularly strong quarter with sales up 138% year to year,  thanks in large part to its new touchscreen Omnia. See Gartner’s Q4 2008 table below.

Below the fold: Gartner’s tables for smartphone operating systems for the year 2008 and for Q4 2008.

Note: Google’s GOOG Android operating platform is recorded in the Linux category, where it accounted for 20% of Linux smartphone sales in Q4, according to Gartner. Microsoft’s MSFT Windows Mobile share includes smartphones sold by Samsung, HTC and others.