Many comments here are interesting (i've not read all of them !). Sure many people speaking here are really game lovers and it's good ;-p ... a game lover say GAMEPLAY before !!!!! in fact it's quite normal as poor gameplay games go too soon to trash to stay in memory ;-p
Html5 games creation is quite different for classic games. When creating a classic game graphics are really the most important "first" for 90% of games ... and people waiting for a new game only seeing 3 screenshoots can't say it's not true !! .... so a game is unplayable in early state of creation unless using last computers on market and last high cost graphics cards and so on ... but as this game will be finished in 1 or 2 years ... sometimes more ... it should be will be very playable when published ;-p
For a html5 game which can be created in a couple of days/months is really different. As acord say graphics are important to bring first interest in game ... but obviously a game which can make you spend hours and days in it can't be "only" a beautiful game and so for that gameplay is needed (not only fps but also game "thinking" for players pleasure when playing).
So we have game thinking for looking pleasure and game thinking for playing pleasure ...
Some games "creator" have made the choice to "sell" games with poor gameplay a so very short life but with very good graphics to bring interest until going to trash very soon ... for me it's more games sellers than games creators but it could work too as the players profile deeply change in a couple of years ... hard core gaming is quite over ... so quick played and dir... beautiful games ;-p can find players too ;-p
The best stay graphics and gameplay, if not possible it is the way you want this game will be played and targetting players profile which help you to find the better choice.