There is plenty of argument about what constitutes the best Classical Guitar, however there is some general agreement. The best instruments are made with hardwood backs and sides (mahogany or rosewood) and a more flexible face board usually cedar or spruce. The neck of the instrument is usually made of rosewood, maple or ebony. It is common in Classical Guitars to make the neck of a cheaper wood such as maple and to front it with a fingerboard made of rosewood or ebony into which the frets are set. Some guitars are quite elaborately decorated with mother of pearl or ivory used to mark the main playing positions (the positions marked vary from make to make) but usually the 5th 7th and 12th frets are marked. Many Classical Guitars appear to have no position markers, but in these cases it is customary to mark the positions on the left side of the fingerboard so the player can see the positions but the audience can not.
The question as to which guitar is best is of course an aesthetic one as each player and each listener will prefer different aspects. A good guide is the hardness and stiffness of the materials used the harder the woods the more strident and bright the music that is produced. Some people will prefer the clearer and brighter sound of the harder woods and some the softer and more mellow tones of the softer woods. What is without question though is that the cleaner the manufacturing processes and the higher the quality of the workmanship the better any particular instrument will sound, and of course since they are made of natural materials no two will ever sound quite identical!
This said most people believe that the best guitars for Classical Players are those made by the Ramirez family, but for those of that can not afford a truly hand made and crafted instrument, those guitars made by Yamaha are excellent factory produced examples. The Yamaha process is one of supreme accuracy in cutting and preparing all of the parts and when you inspect any of their instruments the gluing is delicately and precisely done and there is great attention to detail.
My first guitar a Yamaha CG 100 A actually had better tone than one of my tutors hand made guitars from Germany! That cost many times its price. Westwood, Washburn, Alvarez and Hohner are also manufacturers that make excellent mass produced instruments. It should be noted that Yamaha now also make hand crafted top end instruments that are very hard to beat in terms of value for money.