Yeah, rnlf also mentioned on IRC that the side-scrolling thing is a very significant step forward for DOS.
I never realised at the time that this is very different from how for example Prince of Persia or Another World/Out of this World work. To me, all these games played very similar and by comparison, Commander Keen definitely isn’t the best looking one.
I never was a big fan of the platformer genre in general, but thinking about it for a moment, I did play more DOS platformers than I thought I did. Apart from the already mentioned Prince of Persia and Another World, I especially enjoyed Blizzard’s Blackthorne, Jazz Jackrabbit and the Disney platformers (Aladdin and The Lion King). Those games can compete with the best console platformers imho, but of course they were released years later than Keen.
So even though Keen might not make the best first impression compared to contemporary games in the same genre, it did pave the way for scrolling DOS games. We have to respect that I suppose, haha.