The power of Thanatos

Frankenstein's drive (and therefore downfall) isn't ambition; it's his death instinct. Simply put, Frankenstein wants to die, and his entire twisted story is merely a means to that end.

Consider how he relates his feelings. He speaks in maudlin hyperbole—either he's at heights of happiness unknown to other mortals, or his despair defies description. In Chapter II, he says, rather immodestly, "No human being could have passed a happier childhood than myself" (Shelley 39). Right. And no human being would express happiness so pompously. However, Frankenstein's happiness proves short-lived and he spends the rest of his tale bemoaning his fate. A fairly typical example reads, "...my general state of feeling was a torpor, in which a prison was as welcome a residence as the divinest scene in nature; and these fits were seldom interrupted but by paroxysms of anguish and despair" (Shelley 187).

Such extremes of feeling, repeated ad nauseam as they are, are clearly a ruse to disguise Frankenstein's true plan: self-destruction. The creature may as well not even literally exist; it is, after all, a mere surrogate for Frankenstein's desire to end himself. How could he possibly think that creating a hulking, sentient corpse-man wouldn't cause him any problems? How could he practically dare the creature to kill his fiancée by tearing up its bride to be? Frankenstein's actions aren't those of a man seeking happiness—happiness was handed to him all his life but he refused it. He instead sought a means to destroy that happiness, and ultimately himself.

So when asking the question of whether or not Frankenstein succeeds, it's important to understand his true goal. With that in mind, he succeeds marvelously. The creature is his instrument; he never loses control of it. It doesn't turn on its master; he grooms it to be his executioner from the beginning. So why not just go for a more time-honored method of suicide? Simply put, Frankenstein is too weak. He needs a proxy because it allows him a moral escape hatch, a hiding place for his essential cowardice. Killing himself in a more pedestrian fashion would disappoint his family and friends, and he clearly doesn't have the nerve to do so directly.
Thus he creates his creature; he gives life to death to give death to life.