Licensed PAL NES games not released in North America, total 35 games
Asterix (I thought this was announced for NA, but maybe it was the also PAL-only SNES game I was thinking of. But no NTSC ROM regardless.)
Aussie Rules Footy
Banana Prince (DE/JP)
Beauty & the Beast (announced for NA, but never released)
Championship Rally (AU, Exciting Rally in JP)
Crackout (FDS port)
Devil World (SCN/JP)
F-1 Sensation (EU/JP)
Hammerin' Harry (Daiku no Gensan JP)
Konami Hyper Soccer
Legend of Prince Valient
Les Chevaliers du Zodiaque (FR Saint Seiya: Ougon Densetsu)
Mario Bros. (Classic Serie)
Mr. Gimmick (SCN/JP)
New Ghostbusters II (Many know this is different than Activision's Ghostbusters II. I think EU got both games. EU/JP, NA prototype ROM exists.)
Over Horizon (EU/JP)
Parasol Stars: The Story of Bubble Bobble III
Rackets & Rivals
Rainbow Islands (Ocean's PAL version is different that Taito's NTSC versions)
Road Fighter (SLIGHTLY better graphics than JP version, still not sure what Konami was thinking releasing such a simple game seven years after the Famicom version)
Rodland (ES/IT/JP only?)
Super Mario Bros./Nintendo World Cup/Tetris
Tecmo World Cup Soccer (not the same game as Tecmo Cup Soccer Game aka Captain Tsubasa)
Trolls in Crazyland (EU and JP. Announced and canceled both without and with the Trolls license for NA. Can't remember if a proto ROM of either version ever got released.)
The Japanese and PAL versions of Dragon's Lair both use VROM in place of VRAM in the NA version, which reduces the slowdown. But for some reason the Japanese version put jump on the Up button, which is even more annoying than pressing B.
I do have a copy of the Ocean version of Rainbow Islands, and I played it on my top-loader NES. Strangely the music actually sounds better at the wrong speed.
Though I haven't played it enough, I suspect that playing on an NTSC console will result in the timer ticking faster than it should.
EDIT: How could I forgot Rodland, what was once considered the rarest PAL game (not sure how it actually ranks compared to Mr. Gimmick).
And I forgot Dropzone! I briefly had that cart as well in a shipping mixup. That one would need an NTSC fix. In the HUD, half the scanlines for the score font are missing.