In the search for tea excellence, I think you can define two paths that people take:
1. The Whoaaaaah teas
These teas are like fireworks mostly in your nose and sometimes in your mouth too. Their fragrance is usually intense and they display very exotic and complex aromas. But, except for puerh, these teas tire rather quickly after a few brews. The way to brew such teas is strong: above average quantity of dry leaves and shorter brewing times to control the astringency and the bitterness.
Such teas are quite straightforward to appretiate. They are like an action movie with lots of explosions and stunts that keep you riveted on your chair. Good examples of such teas on my selection would include the 2004 raw Yunnan Puerh and the 2001 wild raw Yi Wu Puerh from Fuhai. Jinxhuan oolong can also often be classified as such a tea.
Of course, quality can vary greatly in this category, with the lowest quality typically being the scented teas. There are also very good such 'Whoaaaaah' teas, like light oxidized, high grade Tie Guan Yin. It's also a question of mood, setting and preference: if your spirit can't completely focus on the tea, then such teas are very fitting (for instance, when you drink with many friends together or with the kids around).
2. The 'Hummmmm' teas
The very best teas I have drunk didn't excite me, they were soothing. The first sip is like fresh, pure spring water. It just slips down the throat as if this were his home. Then, slowly and tenderly the mouth is filled with a very balanced, long and lingering aftertaste that feels like a long kiss. The fragrance is very pure, rich and deep.
The feeling you get from such an experience is one of calm and quiet bliss. If the above teas are action movies, than these 'Hummmmm' teas are like Somerset Maugham novels: you enter a new world, enjoy every sentence and come out with a better understanding of human life.
Such are the teas I enjoy most and that I try to select. The best example I can give is my 2003 Yi Wu wild raw puerh. Another example is high quality Lung Jing. Very few leaves, brewed for a longer time, will produce exquisitely light, but rich teas.
Here lies a difference between wine and tea. Concentration in wine is often a very good sign of quality: the producer has reduced its yield so as to produce grapes with more flavor. This in turn produces a wine with richer aromas. But with tea, concentration can be increased and influenced with the brewing technique (that's also why tea is so much more interesting than wine: there is only 1 wine in your bottle, but so many different results you can obtain with tea).
What tea and wine have in common though, is that the very best ones are not only characterized by nice flavors, but also but neverending afterastes. They never really disappear, but always stay somewhere in your mouth before entering your memory and heart.