Filmography

Detailed below are few clips from films and tv series of the Scooby Doo Franchise as seen throughout time.  

A side by Side comparison of the Original Scooby Doo Theme song with the newest release in the Scooby Franchise, the movie "Scoob," which features infamous super hero the Blue Falcon and his trusty sidekick Dynomutt!!
The First episode aired in September of 1969.  This video is a compilation of the Gangs first season of unmasking nefarious villains on nationwide television.
Released in 1977, this short series features all 45 characters of the Hanna-Barbera Animations.  Bringing together iconic personalities such as the Blue Falcon, and Dynomutt, Captain Caveman, Muttly, and Dick Dastardly.  This series, though created many years prior, runs a lot like the known tv series "The Amazing Race."  Created during the height of the Hanna-Barbera Productions era as Saturday morning cartoon tycoons, this series has all the loved antics and slap stick humor that Hanna-Barbera is known to bring to its audiences.  
Released in 1988, this film is a spin off of the original series.  Featuring Scooby Doo, Scrappy Doo, Shaggy and his girlfriend.  Released during the time of the second-wave feminist movement.  A women's movement that centralized on women's independence and the push away from gender normative roles in society.  The line in this clip "His adorable but Liberated Girlfriend Googie." was an intentional add-in for the times.
Released in 1988 this series ran until 1991.  It was the last Scooby Doo series created by Hanna Barbera Animation.  This doesn't mean that Hanna-Barbera no longer produced Scooby Doo shows, in fact they started releasing the first cartoon movies for the Scooby Franchise, the first one being Scooby Doo meets the Boo Brothers!  Scooby Doo would not come back to the screen as an episode based format until the release of "What's New Scooby Doo" produced by Warner Brothers Animation, in 2002.
Released in 2002.  This series was the first produced series from Warner Brothers after the death of William Hanna.  Hanna-Barbera had been acquired by Warner Brothers through the sale of the Turner Broadcasting System in 1996 which owned Cartoon Network and Hanna-Barbera.  After the sale Warner Brothers allowed Hanna-Barbera to maintain artistic control of their cartoon franchises, but after the death of William Hanna in 2001 Warner Brothers took over control of design and creation rights to the Scooby Doo Franchise.  They updated the designs and graphics, releasing the new Scooby Doo show with a new theme song that was played by a known popular band of the time, Simple Plan.
This is the 14th film in the direct-to-disc release format from the Scooby Doo Franchise.  Produced by Warner Brother Studios, this film shows the change in graphic design that can be seen in comparison to the release of "What´s New Scooby Doo," in 2002.  Also, as should be noted, since the turn of the century, Scooby Doo shows and movies have featured up to date technological advancements, such as the GPS in this clip, and the known challenges that goes with those changes.  During the time of this movies release the seventh movie in the Harry Potter octology had hit theatres, giving a boost in the pop culture 'wizarding craze'.  The chosen theme for this movie fit well with the pop culture focus of early 2000's.
More Meddling!
This list of videos is but a small dip into a very large and deep pond.  I displayed these specific shows through time to give clear examples of the creation changes made to fit into the times in which each tv show or movie was released.  
Also, This brief animation timeline shows the design and graphic changes as the technology of the animation world changed from the 60s into the CGI world of today.  Though I did not display the live action films of Scooby Doo first released in 2002, it goes without saying that the CGI designs of Scooby Doo in the film were good for the era of technology in which its was produced.  
A clear indication of changing animation styles can be seen in the jump from the 1988 "Pup Named Scooby Doo" to the 2002 release of the "Whats New Scooby Doo" series.  A notable change can also be seen in the jump from the 2002 Scooby Series to the 2010 release of Abrcadabra Doo.  The animation industry continues to evolve, and Scooby maintains it relevance not only in materials but in production quality as well.

All sources listed here came from one website, source is listed below.

“Internet Archive: Digital Library of Free & Borrowable Texts, Movies, Music & Wayback Machine.” Internet Archive: Digital Library of Free & Borrowable Texts, Movies, Music & Wayback Machine, January 1, 2000. https://archive.org/.