Pascal's Wager Revisited

[Iroscato]

If Odin is real, you'll go to Valhalla when you die, providing that you slew your enemies and died in battle (for those of you not familiar, Valhalla rocks the most).

Valhalla is an implausible afterlife, as, since the afterlife neither fully preserves nor fully abolishes but transcends, no one would want to slay his "enemies" for all eternity.

Further, what if it were a substantive moral claim to "love one's enemies" and refuse to slay them?

Of course it is, but you have completely failed to outline how the Judeo-Christian version is in any way more plausible. The vikings were pretty much the dominant power in their part of the world for centuries. I bet their warriors felt pretty damn secure in their beliefs each time they saw their enemies get routed before them. Just because christianity and Islam are the two largest relgions in the world now, they most likely won't be in the coming centuries. They will plataeu, decline, and eventually be lost to the annals of the relentless juggernaut that is time, remembered only as subjects of academic interest to the scholars of our descendants.
Religions, like empires, rise and fall with the ages. The people of Rome thought their empires would last forever. Granted, it lasted a VERY long time, but compared to the length our species has been around, it was barely an afterthought.