This interactive LEGO timeline chart shows LEGO theme releases since year 2000.
LEGO Star Wars, Technic, Advanced Models and Duplo have been released every year since 2000. The popular LEGO City theme was introduced in 2005 and has also been released every year since then. LEGO Chima and Minecraft were released in 2013 and are still going strong.
LEGO did make some experiments that weren’t as successful. For example, LEGO Mickey Mouse only existed for one year (2000), LEGO Spybotics (2002) and LEGO Atlantis (2010-2011).
There are also “seasonal” themes that coincide with movie release in that particular year, such as LEGO Avatar (2006), Cars (2011-2012) and the new Jurassic World set (2015).
Another notable theme is the LEGO Mindstorms that was first released in 2011. This theme has not received any new releases since 2013.
The girls oriented LEGO Friends theme was introduced in 2012 and LEGO seems to be committed to it by releasing new sets every year.