Dragon Age: Origins.

The game was huge.
The story was beautifully executed.
The characters were memorable.
The comedy was hilarious.

And none of the successive titles have managed to hit that same height.

Kingdom hearts and Diablo are the first to come to mind. Mostly because the consensus seem to be that the second installment in both of the series are the best. While I think they both lost a lot of what made them special for me.

I like Donkey Kong Country more than the second and third games and even more than the returns games. But here I recognize the more recent installments as being superior and think I enjoy the first title more from nostalgia.

Starcraft is another game that I think lost some of its greatness even if I think the second game handles the different races extremely well I liked the art style, music and sound design of the first game more.

Capcoms JRPG series Breath of Fire feels similar but I like the first installment most. I think it most memorable while later installments are fun but more of the same.

If one only counts the games released in the west the first Fire Emblem released here is the best. I disregard many of later installments because they just aren't like that game.

Honestly, there isn't one that pops out in my head right now ...

And I won't get tempted into a debate that could ensue with "your opinion is wrong, the sequels are better".

Very few. I would say:

• Xenoblade Chronicles (haven't played 3 but not a fan of 2 or X)
• Silent Hill (I know 2 is more popular but that's my take)
• The Last of Us (only 2 games but still)
• The Talos Principle (only 2 games but still)
• Pikmin (best atmosphere hands down)
• Luigi's Mansion (best atmosphere hands down)
• 999: Nine Hours, Nine Persons, Nine Doors (actually the first entry despite the name)
• Overwatch (cheating a bit?)
• Dragon Age: Origins (probably, though I eh actually haven't played the other yet :P)
• Lego Star Wars (2005) (for the whole licensed Lego series)
• Ty the Tazmanian Tiger (yes there are 4 of those)

And most of those are kind of cheap shots. I disagree with many other classic choices like BioShock or StarCraft. SC2 is one of my all time favorites.

The only ones that come to mind right away are Halo CE (the campaign portion, at least), BioShock, Perfect Dark, and Blaster Master.

Banjo Kazooie; absolutely nailed the debut and delivered one of the absolute best of the genre on their first attempt.

Yoshi's Island. Technically not the first Yoshi game, but the de facto start of the Yoshi platforming series, its shadow can still be felt on every new Yoshi game.

Dead Space
Condemned: Criminal Origins
Batman: Arkham Asylum
Final Fight
Banjo-Kazooie
ActRaiser
Battletoads
Earthworm Jim
Bubble Bobble
Double Dragon
Paperboy
Shadowgate
Ufouria: The Saga
Shadow Man
Dead Rising
Bayonetta
Alex Kidd In Miracle World
Axiom Verge
Deadly Premonition
Ender Lilies: Quietus Of The Knights
Gimmick!
Rampage
Lost Planet
Puzzle Quest: Challenge Of The Warlords

Nah Bayo 2 is better and EX Troopers is the best Lost Planet game.

Prove it!