Kirby Superstar Ultra is a remake/enhancement of Kirby Super Star (US) / Kirby's Fun Pak (PAL) for the DS. It's essentially 6 games in 1 (plus a Boss Rush mode), plus the extra goodies in the Ultra remake that bring it up to 8 games plus three Boss Rush modes.
Difficulty goes from stupendously easy (Spring Breeze) to not quite Nintendo Hard, but close enough in
The True Arena
Graphics are fresh and sort of emulate the SNES ones but with a modern touchup. Lots of abilities, and the presence of Helpers makes it lots of fun. (e.g. Knuckle Joe, an Assist Trophy in Brawl, is one possible Helper who represents Fighter ability).