Yeah PayPal is popular becoz they have good fraud tracking system n blah blah, but pp not support my country.
Haven't used Alertpay, but I do use Moneybookers on one of my e-commerce websites. They are OK, but not as good as Paypal. They have a very lazy customer support system (merchant support).
i used paypal, alertpay and moneybookers. i rate paypal as best next is moneybookers and at last alertpay.
moneybookers is a good alternative and i m using it since 3 years . faced no problem at all alertpay is ok but only used mostly by get paid to websites which are most time scams so alertpay is pretty much useless