If you are talking solo career then every rapper u already mentioned is the correct answer....If u are talking overall....
93 was shared by Naughty By nature, Onyx, Cypress Hill, 2pac, Dre , Ice Cube with Wu tang at the end....So Snoop couldnt really dominate 93
Fugees was to strong for Pac to dominate 96 but his death did help
97 was a Bad Boy year..with No Limit and The Wu coming in 2nd place
98 was Lauryn Hills , DMX and Jay.
02 started off as a Rocafella Year and ended with Em
03 started with 50 and ended with Outkast
08 was all Lil wayne....TI was doing his thing but Lil Wayne dominated 08
The answer to the "overall" is Lil Wayne.