My personal opinion is that the NES was lacking in some respects (EG Graphics) but seemed to have games with more depth to them.
The Master System was technically superior but didn't have all that many in-depth games but most were easy to get into and good for a quick fix of gaming.
(and yes, there are exceptions to that general rule!)
Both were good systems in their own right though and both systems are worth playing each with unique and great titles.
BTW, my backside hurts sitting on this fence!