I don't like the first Snowspeeder at all.
*puts up ultra-mega flame shield*
"Oh yeah, well I have a dog that eats ultra-mega flame shields."
I've read a lot of valid and compelling arguments and I've thought about three years in particular: 1999, 2006, and 2008. Each of the three are touchstones in terms of novelty, quality, and overall value.
1999 - Besides being the first year of production, Lego gave us many of the iconic ships from the OT. For a first year they did a bang up job. X-Wing, DV's TIE, Snowspeeder, Landspeeder, Speeder Bikes. Even the lowly Y-Wing. The figures accompanying the sets were also great outside of waiting for Han, Leia, Chewie, and C-3PO until 2000. The one faulty thing from the whole year is the number of Episode One sets that came out instead of OT but I understand why they were released from a marketing standpoint. Even the EP1 sets were great and you could get all of the big characters in the cheaper sets (Qui-Gon/DM in Lightsaber Duel, Jar Jar in Swamp, Anakin and Padme in Anakin's Podracer) except for OB1 (Gungan Sub). If you also look at the cost per piece (cpp) ratio they were OK, just slightly over 10 cents with the more intricate Gungan Sub at $0.13/part. What was so great about 1999 is that these were alternates to Hasbro toys; some of which were tough to find at times. The Gungan Sub wasn't literally the one from the movie, but a version that had the Lego spin making it interesting. I never saw a manta ray in EP1, but one came with the set. I never saw a battle droid Zamboni, but one came with the Naboo Starfighter. Plus I have one word...Snowspeeder
, to this day my favorite of all the sets.
2006 - It's nice to get a large collection of Lego to choose from in any given year but 2006 had quality rather than quantity. There were only seven new sets, eight with the X-Wing rerelease (not counting UCS sets). Other than a movie year (1999, 2002, 2005) this is the last year where there was a smaller amount of sets, if MINI sets are not included into the tally. Since 2006 Lego has inundated the shelves with lots of new sets, making it harder for completists to keep up as there is less room per sets on the shelves. All the sets are of good quality with excellent cpp ratios (0.10 or less). One negative about the small number of 2006 sets is the relatively large number of rehashes to new sets (the TIE/I is a neat set but it's not too dissimilar to the other TIE sets). But the A-Wing and B-Wings are good examples of how to do a remake right (e.g., new figures, sleeker designs, not a ton of new styled pieces to drive the price up). The Jabba Barge is a great piece of work as well. Including the prisoner skiff was a nice touch. I have the Star Destroyer but never ended up putting it together so I can't give my testimony on it, but look at how many characters came with both of these sets. What keeps me from making 2006 my favorite year is this was the year that stickers really made their foothold and the introduction of STAMPS. That really gave an otherwise perfect set (Jabba Barge) a big black eye.
2008 - I'll be upfront and say that I abhorred the Clone Wars sets for their prices. The actual cpp ratios aren't too bad except for the Separatist Spider Droid. The crappy TRU trend of pricey exclusives started in 2005 with the Imperial Inspection set (14 cents) but the 7681 has a ccp of 17, really a nice way of getting people to buy a Commander Fox minifig. I still have price issues with the MagnaGuard and V-19 Torrent, but since I've bought them on clearance I've mellowed a bit. I do admit that the wing opening function of the V-19 is a great feat of Lego engineering. Props. The stormtrooper and rebel trooper army builder sets are great (still at the $9.99 price point before the leap to $10.99) and so are the Republic Fighter Tank (my favorite exclusive set--thank heaven Target got this one), Ani's Starfighter, the CW Gunship, and the holy grail of Lego sets, the Death Star (mine should be here by tomorrow!). I dislike so many different sets in one year, and 2008 really got the ball rolling for sheer numbers of sets, but there were a good number of interesting things that were released. Overall, there isn't one set from this year other than 7681 with a high cpp--even the Death Star is at 11 cents. The amount of stickers wasn't huge either, but there are a good number in the Gunship, though I'm hoping the DS has very little.
It's a tough choice, but I'll through my hat in the ring with the other alter kakers and give my vote to 1999.