What is a great poetry?

The lazy sunday had been kind of productive for some fancy new ideas :-) After falling in love with the rather haunting song, I was thinking what really makes a great poetry?

I agree the answers to this are going to be largely personal, I am just trying to thing what I perceive as a Good Poetry.

To me I think it is something like this "You understand every word of the poem, every sentence of it, but don't really get oh what is the poet trying to say and almost feel like calling him and asking, "hey what did you mean to say here?"eg. consider this - from the famous बीडी song -

ना बुलाया ना बताया माने नींद से जगाया मर गयी|
ऐसा चौंखे लिहाफ़ में नसीब आ गया
वोह इलायची खिलायके करीब आ गया|

now I just couldn't get the meaning of this... or even

जो भी कहां उस चंद्रभान ने फट से हो गयी राजी मैं|

now why does the lyricist wants to use the word चंद्रभान?

When I really get these questions, I start liking the it.. eg. consider another one (and for a change this is not one of the haunting types but a bit of religios marathi song)

पिते दूध डोळे मिटूनी जात मांजराची मनी चोरट्याच्या कारे भिती चंदण्यांची

सरावल्या हातांनाही कंप का सुटावा? उघड दार देवा आता उघड दार देवा....

this one is by ग. दि. माडगुळकर.

PS: I used to use ScratchPad for typing marathi or hindi words, till aditya said to me, I use it to write even in english.. After trying it myself, I think I will never use blogger editor again.