food for thought 1-a work of art!!

how does one rate paintings??
I have not done a course on critiquing; nor have friends who understood modern art i have'nt googled how paintings are rated ( yet!)...i was looking for an interesting topic to blog on and presto !! this question has befuddled me for quite a while...with the old classics the artist would paint forms which were objective...smting you had seen in real life or could relate too- lady maddona with a child..landscape,boat by the sea,lord krishna on a swing...forms which could be compared to real life visuals...you probably could appreciate the brush stroke...the colours used..the emotions on the face of portraits...then came the renoir's and bunch who made it slightly difficult to interpret there work but all in all you could understand they were painting a house;fruit bowl or portrait...with the surreal movement and others since( i know not much about) all i see of modern art is arbit pieces of work...life forms with mixed limbs;a few brush strokes on a white sheet which could be interpreted as and how u see it??
i personally feel that what appeals to your sense of aesthetics should be accepted as a good piece of art...but then how would you price somthing like that??? on whos basis do we evaluate one artists work as genius and the others as a farce??
people mostly follow the herd mentality waiting for one artists claim to fame from an accomplished critique and shower praise; appreciate beauty of the work on foundations of the critiques acceptance of the same!!