What is a good base for a generator mechanic to be stationed?

As a 91D, you should use your reenlistment window to reclass. Preferably 91B if you enjoy being a Generator Mechanic. Once you make SGT you're going to get stuck for a long time trying to make SSG. Pretty soon you'll be in for too long to be able to reclass and you'll be an 11 year E5 looking down the barrel of RCP and ineligible to take advantage of the Blended Retirement System Continuation Pay

You have a broad selection of most any base in the Arsenal, as long as your grade is open. Check the system and speak to your retention NCO and or Branch to see what is available.

As for choices that is based on likes and dislikes, hobbies etc. i personally would select a base based on what I thought of the area. Do sone research and good luck.

A good base and bad base is relative. It completely depends on the person. That is the same thing for any base and any branch. I have met plenty of Airmen who enjoyed being at Minot and some who absolutely hated it. The same goes for Alaska. Some people don't mind the cold and love being in those robust landscapes. Other folks hate being in the desert while others are extremely happy. Being close to family is a bonus for folks, being close to sports or activities they enjoy can be a factor as well. If you dig kayaks and snorkeling Hawaii is a dream land while others get island fever within a week. It is all on you and what you like/dislike.