I definitely loved playing through DK1, but there's something about DK2 that's always held my interest for way longer. I will say I still haven't played DK3 - I didn't have access to it as a kid.
Both games are great so it's not hard to say they have both are great games. DKC3 is pretty much the same as the other 2 just different style and designs/themes. I think ya can get it on Virtual Console if you have a Wii U. It a fun game and I think it's the hardest out of the three.