Personally, I prefer Mega Bloks. Their blocks might not be as good a quality as Lego's blocks, but their sets are very cool. Their Dragons fantasy line has actual orcs! I've been collecting them for use as skirmish miniatures, and they are very cool. While Lego people have the typical Lego yellow, round heads, Mega Bloks' fantasy figures have human (or orc) faces, Viking like ships with rounded hulls and fabric sails, and very cool rock formations. We have used their Alien Agency line (think "men in black" and Majestic-12) as Delta Green miniatures. I want to get one of their more complicated military sets at some point.
Lego sued Mega Bloks in Canada, with the suit finally coming to its completion with the Supreme Court of Canada this week. Lego's patents had been expiring since the 70s, and the last of its patents expired in Canada in 1988. They sued Mega Bloks claiming trademark infringement. Their argument was that the look and feel of plastic stackable blocks was part of Lego's trademark. They claimed the bumps on the blocks (which allow them to connect) was an intrinsic part of Lego's trademark. The Canadian Supreme Court, in a unanimous decision, declared otherwise. The Supreme Court said,
..."purely functional" features, such as the well-known geometrical pattern of raised studs on the top of the bricks, could not be the basis of a trademark.
Trademark law should not be used to perpetuate monopoly rights enjoyed under now-expired patents...
They continued with:
The fact is ... that the monopoly on the bricks is over, and Mega Bloks and Lego bricks may be interchangeable in the bins of the playrooms of the nation – dragons, castles and knights may be designed with them, without any distinction.
This isn't the first dispute between Canada and Denmark. Both claim tiny Hans Island, between Ellesmere Island and Greenland. It's unlikely to result in a shooting war, and it's been called "a friendly dispute". Here's a story on the island from the CBC News site: www.cbc.ca/story/canada/national/