is a 29er a good fit for a 5'9 height? I'm a 5'9.5 and I use a 26er gt and I don't feel that comfortable as it feels so small. I've also tried a 27.5 merida, it was an improvement but I can't still quite grasp that same feeling when you were a kid and bikes were huge. I feel a 29er would be better for what I'm craving for, but since I've been hearing about 29ers being sluggish, for a guy who loves single tracks, would buying a 29er which is slightly more expensive a choice to regret?

BTW I live in a city where there are limited bike shops, and they don't give test rides. So please help me. I don't want to spend my budget on something I really want and then regret it. An answer from someone who already had or have a 29er would be great, but anyone would be appreciated.
I would say it depends on your riding style and the geometry of the specific bike you are looking at.  29'r is definitely not to big for you (I am 5'10" and my 29'rs are just fine).  However, there are reasons that a lot of all mountain, freeride and almost all downhill rigs are still 26".  29'rs are less suited for highly technical riding, but much better suited for cross country and trail riding.  As always, tailor your bicycle choice to your riding style.  

If you are into flowy single track and aren't hitting drops, ripping through rock gardens and generally abusing the landscape with your rig, then 29" is probably a better choice for you (with the right size frame).