First 50:
51. Ys: The Vanished Omens (Sega Master System)
52. Code of Princess (3DS)
53. Ys (PSP - Ys I & II Chronicles)
54. Ys II (PSP - Ys I & II Chronicles)
55. Shadow Dancer: The Secret of Shinobi (PSP - Sega Genesis Collection)
56. Gradius (PSP - Gradius Collection)
57. Shinobi (Xbox 360 - Sonic's Ultimate Genesis Collection)
58. Otomedius Excellent (Xbox 360)
59. Deathsmiles (Xbox 360)
60. Sonic the Hedgehog (Xbox 360 - Sonic's Ultimate Genesis Collection)
61. The Lost Vikings (SNES)
62. The Lost Vikings (Genesis)
63. Final Fantasy II (Game Boy Advance - Final Fantasy I & II: Dawn of Souls)
64. Final Fight (PSP - Capcom Classics Collection Remixed)
65. Alien Syndrome (PlayStation 2 - Sega Classics Collection)
66. Exile (Genesis)
67. Ristar (Xbox 360 - Sonic's Ultimate Genesis Collection)
68. Final Fight (Xbox 360 - Capcom Digital Collection)
69. Classic NES Series: Zelda II: The Adventure of Link (Game Boy Advance)
70. Classic NES Series: Metroid (Game Boy Advance)
71. Castlevania: Symphony of the Night (Xbox 360 - Konami Classics Vol. 1)
72. Ys (DS - Legacy of Ys: Books I & II)
73. Ys II (DS - Legacy of Ys: Books I & II)
74. New Super Mario Bros. (DS)
75. Sonic the Hedgehog 2 (PSP - Sega Genesis Collection)
76. Golden Axe III (PSP - Sega Genesis Collection)
77. Muramasa Rebirth (Vita)
78. Magic Sword (PSP - Capcom Classics Collection Remixed)
79. Mega Twins (PSP - Capcom Classics Collection Remixed)
80. Super Mario 3D Land (3DS)
81. Super Mario Bros. Deluxe (Game Boy Color)
82. Dungeons & Dragons: Tower of Doom (PlayStation 3 - Dungeons & Dragons: Mystara Eiyuu Senki)
83. Dungeons & Dragons: Shadow Over Mystara (PlayStation 3 - Dungeons & Dragons: Mystara Eiyuu Senki)
84. Ys III: Wanderers from Ys (SNES)
85. Ys III: Wanderers from Ys (Genesis)
86. Ys: The Oath in Felghana (PSP)
87. Sonic the Hedgehog 3 (Xbox 360 - Sonic's Ultimate Genesis Collection)
88. Contra (NES)
89. Sonic & Knuckles (Xbox 360 - Sonic's Ultimate Genesis Collection)
90. New Super Mario Bros. Wii (Wii)
91. Ys IV: Mask of the Sun (Super Famicom)
92. Ys IV: The Dawn of Ys (PC Engine CD)
Not trying to pull a fast one here. There were two different Ys IV games, both released in 1993 about a month apart. Tonkin House developed Mask of the Sun and Hudson handled The Dawn of Ys. Falcom provided the basic "framework" for both games - so what we essentially have is two completely different games both based off of the same source material, basic character designs, plot elements, etc. It's pretty neat.
Mask of the Sun marks the return of the top-down style gameplay. The bump battle system has been improved quite a bit - you can
feel the hits and get jostled around while taking damage. This leads to fewer cheap deaths and much more balanced gameplay overall. Unfortunately Adol can still only walk in four directions so some of the boss battles are a bit of a slog.
Graphically the game is a bit of a let-down. Despite being released in 1993 it looks like a very early SNES game. It's all a bit grainy and dull looking. Additionally there are no character portraits, which are a staple in most every other Ys game. The three(-ish) cutscenes are pretty sweet though. The game is linear and hand-holding to a fault towards the beginning but then "opens up" and (somewhat annoyingly) becomes one of those "linear of you actually know where you're going" RPGs. Walkthrough highly recommended.
The music is exquisite as one expects from this series.
The Dawn of Ys is a lot like Mask of the Sun, but simply superior in every way. Better graphics, smoother character movement, longer and more varied dungeons, loads of cutscenes and dialogue (well, to be fair that sort of thing isn't possible on the Super Famicom). If you have to pick one (classic) Ys IV game, go with this one.
Onward to Memories of Celceta!