You are not going to beat the adoption of PayPal by the public.
So any other platform will result in a poorer conversion rate.
However if you have to choose something other than paypal, or want to integrate a seperate 3rd party for credit card transactions then I would choose either WePay, Skrill, or Stripe (dependant upon your needs of course)
Freelancer.com have a huge amount of Bangladeshi freelancers and they use Skrill to pay them out. So maybe Skrill is best suited to accept payments from Bangladesh. I'm not entirely sure though as I don't have experience with payments to this country. I just did a little bit of searching.
Paypal is the best. But if Paypal do not support your country than you can take a look on Skrill and Payonner. I have used both of them and I am happy with their service. Payonner has wide range of coverage than Skrill.
I always notice paypal, paypal, but, you have to know that there are other electronic bank more preferable than PayPal, so The top bank in my opnion and which I treat with her for a long time is : Neteller bank really realy so good.
I see Google Wallet as the main competitor in this case, for a few reasons that this software has:
1) Low balance alerts lets you know when you're out of money.
2) Automatic transfer
3) Also, it tracks all the purchases
4) You get a physical card as well, which remains the traditional payment
5) There is a possibility to advertsing
I had been developing the payment system in my previous employment and we do provide a few payment methods for the users to 'Go Premium'. Coding wise I will suggest MOLPOINTS as its implementation is similar to paypal and can be easily adopted into same class of payment verification in the project.