Well, as for my thoughts, what's even many shows I think so far:
The X's (The show only lasted for one season.)
Pelswick (Nickelodeon, Nicktoons and CBC seems refused to air and rerun the show.)
Baby Blues (animated series; the show has been taken off on The WB after 8 episodes, the last 5 episodes aired in 2002 on Cartoon Network's Adult Swim.)
Meeow! (Why the show nevered aired in the USA and Canada.)
Cyborg kuro-chan (The show never get an US english dub of the anime, they nevered aired in the US.)
Animal Yokocho (There was an english dub to the show only on philippines, they never dubbed in US english and why they never aired the anime in the US.)
The Cramp Twins (Cartoon Network Europe doesn't make any sense for the show, but 4KidsTV does this.)
Nontan (the franchise was nevered overseas for many books and others, the anime series of the franchise nevered get many dubs including english, spanish, german, etc. Also the CGI direct to video anime series nevered get many dubs of this.)
Sooty (franchise; the franchise was been in the US on Mickey Mouse Club as a skit; but why The Sooty Show, Learn with Sooty series, Sooty & Co, Sooty's Amazing Adventures, Sooty Heights, the 2001 Sooty series, the 2011 Sooty series and others nevered been in the US and Canada.)
Doris (Hilary Hayton cartoon; the show was even lost, nevered picked up in the US, Canada, Japan, etc. The show was just a cut-out animation.)
Puppydog Tales (1992 series; the show only last for 13 episodes. like Doris, the show was even still lost.)
Mr. Men and Little Miss (1995 france-british animated series; In 1997, they did the US dub for all complete episodes, this nevered been in reruns since then like Class of 3000.)
Peg + Cat (The show ran for five years, that was a really good end...)
Astroblast! (The very last Soup2Nuts production, the show's animation was very similar to last three seasons of Home Movies and WordGirl (also both produced by Soup2Nuts), the show only had one season, some child characters are voiced by adults. Pretty catchy.)