I like training 3 days a week. Because of my job, rest, nutrition, work capacity, and training style, it's worked well for me using a couple of different training methods.
What you need to assess first is not how many days you should train, but where you are on a Novice to Elite continuum, and what your short and long term goals are. An Elite level Olympic Weightlifter would most likely train 6 days a week. A Novice might be very well served to train just twice.