I actually forward my GMail to Outlook and have always gotten my mail instantly (or within a minute or 2). I used the Outlook.com to "pull" my existing mail in (that part takes forever, so be patient) and then setup GMail's forward option to push incoming mail to Outlook.com - this has been working great for me.
Again, that only works as fast as gmail pulls in your email. If you need to have your pop email on your phone, of course, you can set it up as a separate account, but the quickest it will check is every 15 minutes and that will use extra battery life. If your pop email has imap, you can set up an external imap server to push your email to your phone almost immediately. I'm sure there are others, but I use nuevasync.com and it does a very good job with imap email, almost instant response. Yes, it costs $30/year and yes, you shouldn't have to pay for this functionality because it "should" be built into Windows phone. But it isn't so for now, that is the best option.