I'm pretty new to backpacking, but from what I've read/learned, I wouldn't think there is any one best pack to get. There's several brands making good packs, and the variances between any two different people make for a lot of variability in which brands make packs good for any particular person. Then there's the goals of that person that further influence which brands and which packs within a brand are good.
If you have access to a bigger camping/outdoors shop to try things on, get the pack fitted, and wander around the store wearing it with some weight in it, that would probably give you a good place to start.
Beyond that, how much gear do you tend to carry? Do you have a budget? How long do you tend to stay out when you go? What activities do you enjoy doing while out: do you tend to go out and base camp for a bit, do long marches and cover lots of miles? What kind of trips you make adds in a lot of variability on what you would want in a pack for your trip!
So, do you have any further details about the kinds of trips you're taking, how long they last, and what you enjoy doing while out? That would go a long way to helping get decent recommendations!
If you're unfamiliar with them: Moosejaw, Backcountry, Garage Grown Gear, and REI are some pretty good sites for new equipment, and REI tends to have physical locations in various places around the country too, as well as periodic "garage sales" of used equipment. There is also Geartrade to buy used or overstock equipment from both retailers and direct from consumers.
Hope you're having fun out there!