Wonder Boy is a neat little action-RPG for the Genesis. That is not to say that it brims with innovation, or blinds with graphics, or deafens with brilliant orchestral scores. Its grace is the fact that it begins, goes through all the possible permutations, and then STOPS.
Wonder boy is light-hearted, though not necessarily humorous. Expect lots of cute foes. Expect clean, colorful sprites and simple dungeons. Expect a lot of generic platforming (e.g., swimming between rows of spikes, jumping from ladder to ladder, outrunning rolling boulders, etc.)
Wonder boy rarely drags, and when it does, it's probably because you are gathering treasure to buy new equipment. In this way, Wonder Boy is slightly unbalanced - sometimes it'll be necessary to wander around for quite a while in order to accumulate enough money to buy a new weapon, or suit of armor, or shield, or a pair of boots (which allow you to run faster and jump farther), and, inevitably, each new village will have a new set.
Luckily, leveling up is impossible here - your health depends on the number of hearts you've found on your journeys. It's no big wonder that combat in Wonder Boy is in real time: it's that simple. Jut your weapon out and you're halfway to victory. You can dodge or jump, or simply catch enemy blows with your shield. Not to say that combat is always easy - the final boss is almost unfairly hard.
The control scheme is as simple - A is for items/magic (magic is restricted by the number of uses, not MP), B is for attacking with your various weapons (which are divided into two groups - swords and pole-arms; shields cannot be used in conjunction with spears and such), and C is for jumping.
There is no overworld. Wonder Boy is unified by the fact that it is all essentially one big dungeon. Bustling cities and simmering jungles border one another.
Just to warn you, Wonder Boy is plotless. Or at least very close to being so, since the only consistent goal throughout the game is to vanquish the dark forces of evil. The rest is simple fragmentary fetch quests that merge one with another - save the dwarf child from the monsters in order to gain passage into the tomb in order to find the trident in order to go to Poseidon, and so on.
Wonder Boy brims with a certain unpretentious honesty: it is nothing more than itself, and it doesn't pretend to be anything other than that. Its only RPG elements are purchasable equipment and items, plus a smattering of spells. This sincere and utter simplicity quickly proves strangely compelling: if it's to your taste, you will finish this fairly short game in no time at all.
Wonder Boy has little replay value - there are a few secret doors to find, and a special item to figure out, and once you are able to shrink, you can backtrack for hidden chests, but beside that, the only reason to play it for the second or third time is to pass the time.