There has been a great deal of improvement in the level of guitar teaching during the last 30 years yet the current state of guitar teaching is still poor in my opinion. This has a lot to do with the history of the guitar in both its classical and popular music tradition. As a classical instrument the guitar has a much richer history than it is given credit for yet it can not compare to the history of the piano and violin and many of the orchestral instruments. Whereas the classical guitar went through periods of popularity in certain cities when a number of virtuosos were active in that city, instruments like the piano and violin enjoyed immense popularity in every city in Europe. One of the high points in the history of the guitar was in the mid 1820's in Paris when the famous guitar performers and composers Fernando Sor, Dionisio Aguado, Ferdinando Carulli, Matteo Carcassi and Napoleon Coste were all active in the city at the same time. Yet this is an insignificant number of top guitar players and composers in Paris when compared to the number of piano or violin performer/composers active in Paris at the time. Additionally, most of the major European cities had piano/violin scenes comparable to that in Paris while in guitar this was an anomaly. The result of this is while several of the above named composers did write guitar methods, for each guitar method produced there were a hundred piano and violin methods produced. The guitar methods often stopped being developed upon the death of their authors while the piano/violin methods developed into schools of playing that were constantly being improved upon. The result was that the piano and violin developed very strong schools for training musicians while the guitar lacked well developed pedagogical methods. It has only been recently that some of the leading guitar teachers have tried to remedy this situation.
The guitar also had a simultaneous existence as an instrument in folk and popular music. However, much of this music was simple and not technically demanding and thus schools of pedagogy were not developed. In the 20th century the guitar became the dominant folk and popular music instrument but again much of this music was simple and not technically demanding. Over time these music forms have developed at least some sub-genres that are more technically demanding, such as heavy metal shredding and virtuoso acoustic fingerpickering, but it has only been recently that methods have been developed for these genres. Again the end result is that guitar pedagogy is lagging behind that of other instruments.
Guitar teaching is superior in one aspect though, the lack of standardized schools has led to a less rigid style of teaching and also more flexibility in teaching various styles. For example, it is more likely that a classical guitar teacher would teach a student some blues or rock songs than for a classical piano or violin teacher to do likewise. Often in comparison to the more difficult and technically demanding repertoire they are teaching it would be easy for a classical piano teacher to teach their students some blues or boogie woogie piano songs yet this is seldom done. This is a shame as it would probably increase the enthusiasm of many students for the instrument. Fortunately, guitar pedagogy for all of its faults is also not so rigid and the student is often able to explore many different styles.
It is hard to find a good teacher of any instrument but a bit harder in guitar than in many other instruments. While there are certainly a lot of guitar teachers the percentage of these teachers who could be considered good teachers is lower than that of most other instruments. This is also true as far as guitar method books and teaching material is concerned. While more and more quality books are appearing one still has to sort through a great deal of poorer quality material to find them. There are good teachers out there but one has to do a bit of searching to find them so I recommend doing an adequate amount of research before deciding who to choose as your teacher.