Sick year!
My two favorite games didn't even get mention. I vote for Vampire The Masquerade: Bloodlines. One of my favorite RPGs of all time, with fantastic writing and characters, exceptional customization and player freedom.

DOOM 3 was another huge leap forward for gaming, when it came to graphics and atmosphere. And while the gameplay was slower than previous entries, it was equally fantstic to play with the more survival horror direction. It's crazy how good the graphics were, remember being amazed by this, Half-Life 2 and Far Cry, it probably took another 3-4 years before that level of graphics became the standard.

Speaking of Half-Life 2, that is obviously another fantastic video game. Halo 2, Second Sight and GTA San Andreas are also honorable mentions.

I wish I had played Hslf life 2. Of these I played San Andreas the most.

Ninja Gaiden was my favorite that year

First I thought I'd vote for MGS3, but then I realized that the first Trails in the Sky was originally released in 2004 in Japan, and I assume we're going with the original release dates, so I'll have to vote for that then.

How do I pick, this feels even harder than 1998 to choose a winner.

Ranked on greatness:

1. Half-Life 2, introducing the gravity gun and physics based puzzles. Brilliant sequel pushing the shooter genre forward.
(Plus shooting toilet bowls and radiators at people in HL2 death match never gets old)
Half-Life 2 also dragged PC into the digital age, tying the most anticipated sequel to Steam was both evil and brilliant.

2. Burnout 3: Takedown, my favorite Burnout game, best hot seat crash junctions as well.
Great selection of tracks next to heated competition over setting the highest scores in crash mode.

3. Paper Mario TTYD: Loved it start to finish, wish it were even longer. Great adventure.

4. World of Warcraft didn't become the biggest MMORPG for nothing, absolute amazing and even had Mario and Luigi make a cameo appearance.
We played this game together for over 3 years, almost daily.

5. GTA: San Andreas, my favorite GTA game, it needs a proper remake. (And maybe I can finish it this time, it got too hard for me)
The way San Andreas opens up is done really well, never overwhelming, yet in the end it's 3 proper towns to play in plus some villages.

6. Gran Turismo 4: First time the Nordschleife appears in its full glory, with 1080i output as well. Still the best campaign for any GT game.
7. MGS3: My favorite Metal Gear Solid game, was even better in the remaster without the fixed camera angles.
8. Far Cry: Amazing when it came out, open world done right, before all the filler clutter took over.
9. Katamari Damacy: Ack the music is stuck in my head again, brilliant concept well executed.
10. Fable: The first one is still my favorite in the series, such a nice surprise at the time. Looked great as well.

Runners up
Doom 3: Actually my favorite Doom game, I enjoyed the slower paced gameplay. Amazing graphics for the time as well.
Jak 3: Great end to the series, however I didn't play it until the ps3 collection. Good games stay good forever.
Ratchet and Clank: Up your arsenal, another great entry, consistently great series.
Halo 2: So much fun playing in co-op.
The Sims 2: Adding genetics to see what your babies could look like


The first 5 are in my all time top 50, tied with 1998 (yet those are a bit higher up in my top 50, 1998 stays on top)
Since the highest in my top 50 for 2004 in HL2, my vote will go there.

Other have to go with Gran Turismo 4 because that is what I played the most. Next two years I will vote for Capcom games the 2005 on should be in the poll and the 2006 one should be in the poll also but might not be.

World of Warcraft probably wins it for the impact, I like Doom 3 but not enough for GotY, I've enjoyed Rome: Total War a notable bit, Metal Gear Solid 3 is a great game in a series I like a lot, but ultimately Half-Life 2 gets my vote. Of all the candidates, it has stood the test of time the best in my opinion (although graphically Doom 3 still beats it by a fair margin).

See, this is what a stacked year looks like, not like the previous 3 years.

I dont know. This is a though one for me. Im biased so im gonna vote WOW because I loved it. Best mmorpg there ever was. There no denying its influence and on a personal level it gave some good years of fun. 

Doom 3 looks fantastic, great use of the flash light and interactive screens! Rendering the screens separately instead of just a bitmap made a huge difference.

Character models weren't so good though and the game slowed down to a crawl in the last act. I had to finish the game on easy as the fps would tank into the lower tens. So I replayed it a few years later on a new GPU able to power through the demanding final act.

HL2 had no performance issues apart from overloading the container while swinging it around with the crane. I played with that for a long time, filling up the shipping container with all kinds of stuff, then swing it around with the crane and watch stuff fly out lol. I don't remember what its purpose was, but it was a lot of fun! Same as filling up chimneys in houses with everything around then chuck a grenade into it. Fun physics.

HL2 looked great as well, reflections, shadows, lighting and character models were ahead of the curve.

Doom 3 had the cleaner image overall, HL2 pushed more boundaries in rendering tech.

Both could use some RTX love, oh already being worked on for HL2

Doom 3 has some reshade mods, not looking anywhere near as good as HL2 RTX (also upgraded textures and models)

1) Half Life 2
2) World Of Warcraft
3) Halo 2

World of Warcraft. You all already know my reasoning.