I'd suggest going from the beginning. Take the good with the bad. I just finished the show myself. Looking back on it all, a lot of the episodes I was critical of in the earlier seasons are much better than I gave them credit for originally. I was extremely harsh on that first season, but I think that has a lot to do with me jumping into VOY immediately after finishing DS9 (there were other reasons too....). It took awhile for me to adapt to the episodic style of VOY, but once I became used to the format I mostly enjoyed it. I personally thought the last two seasons were the strongest (although that view isn't held by many other fans), but there's still plenty to enjoy in the earlier seasons. So, once again, I'd recommend you watch all of it and formulate your own opinions. You might find you really like certain episodes that aren't so popular with the mainstream crowd.