Depends on your criteria, I suppose. Portland has nearly half a million people, and the metropolitan area over one million. That's big enough for most folks. It also has more restaurants, microbreweries and strip joints per capita than any other major metropolitan area in the country. Make of that what you will!
On the other hand, Corvallis has about 50K. That's pretty big by some people's standards, but it's missing a lot of things a city needs, IMO.