Rob at Wind Rose Hotel writes about Pascal's Wager.
Let's apply it to a slightly more complex problem...
Pascal's Wager proves that it's better for you to believe in God, but which God? Each religion offers you one: the benevolent God of Christianity, the harsh, unforgiving God of Islam, the indifferent God (if any) of Taoism and Buddhism, the capricious Gods of Hinduism and Paganism...
Let's extend the reasoning of Pascal's Wager to the case where there's choice between different Gods.
Assume for simplicity the possible choices are: (i) an harsh God (who punishes you unless you believe Him and behave exactly as His Prophets say), (ii) a benevolent God (who may perhaps forgive you if you didn't sin too much or even if you didn't believe in Him -- say you'll end up in Purgatory instead of Hell), and (iii) an indifferent God (who won't neither punish nor reward you -- this case is indistinguishable from the no-God one).
Suppose you choose to believe in the indifferent God, or in no Got at all; then, if the harsh God is the true one, you'll end in Hell (-1 points), if the true God is the benevolent one, you'll probably end in Hell as well, but perhaps not always, depending on your other sins (say -0.9 points). If the true God is indifferent, you have nothing to gain. Total score: -1.9 or so.
Suppose you choose to believe in the benevolent God. Then in the harsh God case you would be punished (-1), and rewarded in the case of a benevolent God (+1). An indifferent God wouldn't care to punish you. Total score: 0
Suppose you choose to believe in the harsh God. Then, if you're right, you'll be rewarded (+1). If the true God is the benevolent one, you'd probably be punished, but perhaps not always (say -0.9 points). In the case of an indifferent God, nothing happens. Total score: 0.1 points.
To summarize, this extended Pascal's Wager confirms the findings of the original one: you'd fare better believing in a God than not believing (or believing in an indifferent one).
Moreover, the harsher the God, the more convenient it is to believe in Him.
So I imagine the best option in the real world, according to Pascal's Wager, would be to convert to Islam, and perhaps hedge the bet by avoiding behavior that's sinful for Christianity (eg. taking more than one wife).