Do you chose a game based on graphics? or gameplay?

Graphics contribute to gameplay, but don't determine it.

gameplay

I like games with a balance between the two, but gameplay will always be superior. Two games that have a great balance are fable 2 and Crysis

Gameplay above graphics, which is why I still play most of my golden oldies. I like to tinker though, so I will spend a lot of time tweaking a game to give me the best visual experience.

For me the answer would be both...

For example I still love the original Elite, which in its day was both ground breaking graphics and gameplay.

I played other games just because they were fun, before we really started judging games by their graphics quality at all

On a gameplay example, I eventually bought Knights of the old republic years after its release purely for the rumoured storyline and gameplay. The graphics were outdated by then but gameplay alone was enough for me to give it a go.

On the graphics side I bought Oblivion and Crysis as soon as they came out - sold by the graphics, seeing the cutting edge of what PC's could do. As luck would have it Oblivion has kept me coming back due to gameplay. Crysis as well but to a lesser degree, people slate crysis but I didnt find the game play of puttingly bad at all.

There are a very few games that stand out in my mind as being graphically innovative and having detrimentally bad game play. Rise of the Robots was a game with huge graphical hype that might have sold better had they never released a playable demo. If there hadnt been a Demo I would have certainly bought it based on the graphics and expected at least passable playability (and been bitterly dissapointed)

I will buy a game either for special technical merit on the graphics side or for exceptional gameplay, but if it has both its likelly to be a long term game for me (like Elite, star wars galaxies and oblivion at release)

I am a graphics junkie, which has led me to a few bad purchases in my time, but yes, graphics are the biggest draw.

Older games are in a place of their own, so graphics matter not, but all modern games that have better gameplay than graphics I tend to avoid simply because i like the Visuals too much!