Which version of Photoshop is the best?

[debasis]

Alensot you are right i am using it because i am working on different types of graphics, e-book and other types of web applications that,s why i need CS3 rather i need the latest version of it, and to learn photoshop completely one need 1 to 2 yrs minimum for getting mastery in it, i have not taken any special course on it but i always play with it and always experiment on each and every controls so i get a basic idea over it.
Thanks.

One should have that interest within him to create new things while working in softwares like photoshop to get more expertise in that

that's right if somebody have no zeal within anything or study anything then he or she can't get any success in it if he or she do the reverse of it then definitely get the success in all field.