Good if your on a budget and you don't want to pay for $15 monthly fees for big MMORPG's like WOW or LOTRO.
Gameplay: Runscape is just like any other MMO, you make a character and lvl him up by doing various missions, create armor or weapons. There are also different Skills which you improve on by doing them more, Ex: You increase your mining lvl by mining more, the higher the LVL in a skill, the more things you can do with that skill. Fights are pretty straightforward, you simply click on an enemy, and you attack, but you can only attack human players in certain areas. The downside to the gameplay is that is can get boring after a while, and there are very few quests you can play as a free member. And the free membership is incredibly limited, blocking off access to most areas and skills and to get the full membership, you have to pay a $5 monthly fee.
Graphics: You can't expect very good graphics from a game that runs off of internet streaming and Java. The graphics give enough to tell what things are but the details are very pour. you cant make out faces on individual faces and roads look like brown lines.
Sound: The game sound effects usually consist of bleeps and bloops, and sloppy clang sounds for swords. The music is in midi format but some of the music is quite creative and catchy.
All in All: If you've run out of options and you're on a budget than this is a good choice. But you can do better player big MMO's