I've always wanted to play that one. I've considered buying a DS in the past for the sole reason of playing NG: DS
I did almost the same, but i bought a 2ds instead since i also wanted to try few 3ds games like DOAD. Glad DS games run on 3ds as well.
Anyways, best momments to me.
1 - Doing the gauntlets i did for one Ninja Gaiden 3 Razor's Edge video i did, I really felt like i was finally able to fight for real in that game.
2 - Finishing all the games on the hardest difficulty for the first time.
3 - Seeing the credits of NGB for the first time.
Worst momments.
1 - Most bosses in NGB on Master Ninja.
2 - Most bosses in NG2.
3 - Most bosses in NG3RE.
3 - Staircase of dropped frames.
4 - Rasetsu and IS gauntlet on M11 of NG2.
5 - Water segments in NG2.
6 - Gigadeath.
7 - Platforming before last boss on NGBlack.