Significance of the switch from Legoland to Lego System?
LEGOLAND

Presumably the decision to discontinue the 'Legoland' series may have been to avoid confusion with the LEGOLAND theme parks.

The original LEGOLAND in Denmark has been open since 1968 and since the opening of the second park LEGOLAND park in Windsor there have been eight new LEGOLAND parks and many LEGOLAND Discovery Centres. 

The planning, design, site preparation and the design and construction of models for LEGOLAND Windsor began in 1992. The same year the LEGO product line disappeared, this however may be a coincidence but it would make sense to avoid confusion between the product line and theme park. The theme parks would also include a product line using the branding 'LEGOLAND' for merchandise such as clothing, books, souvenirs and even some sets based on the parks themselves.

Below you can see two 'LEGOLAND' sets. The set on the left was from the original LEGOLAND series and on the right is a promotional set released for the LEGOLAND parks.





LEGO System

The LEGO® Book1 refers to the LEGO System theme.


  1954 was a year in which Godtfred KirkChristiansen (GKC) did a lot of
  thinking about the future of the LEGO Group. Returning from a toy fair
  in Britain, he got talking to a colleague who pointed out that there
  was no system in the toy industry. That was all the inspiration GKC
  needed. He decided to create a structured system of products.
  Reviewing all the toys made by the company, he saw the LEGO brick was
  the best choice for this project. 


1 Page 18. Lipkowitz, Daniel. The LEGO book. London: Dorling Kindersley, 2012.

The first LEGO System set was actually Town Plan No.