I remember seeing the original series whilst young and young enough to have a memory of everyone having the thundercats bag, the lunch boxes, the toy swords and if it was more fun to watch then He-Man. Thundercats was big and whilst not new in regards to formula it was a different take on the series given it barely included any humans (with exception to Mumm-Ra who i think was human) with striking character designs and a cool sword chant Thundercats was a shining example of a cartoon made marketable.
Looking at Thundercats (185) via youtube and DVD's you see how dated it has become, the writing unbearable sometimes but still the masculine design of Lion-O, Mumm-Ra and the ancient spirits of evil servant 'Pyron' Both have good designs that could be tuned into any show today.
Nonetheless the idea to make a remake was based on the idea that at the core there was a lot the original show could have offered still and this is what the remake does. It goes further much further into detail.
Thundera is now a Kingdom but the cats have lost the moral good to become more muddled, there is genuine rivalry, even dislike between lion-O and Tygra, Lion-O's father prides on posture and is essentially all pride. Other characters have been polished up quite well including the Lizards who are now a race with a strong background.
And cheetah, er wow, she's not bad looking (I'm I confessing to furry here?!)
The voice acting is strong as is the flow of animation. The show reinvents itself whilst being clever with its source material, the writing is very good also.
This series has a great start and will surely have a great run as well. I can see kids who were my age when I first saw the original series be taken in by this as well.
All together now. THUNDERCATS! HO!