That's an easy one. Everything is close to perfect with this album: it's an excellent live record, full of surprises (very good covers), it's nice to hear an electric band unplugged (and it's probably the first prominent example of the genre), Cobain voice is poingant. I'll never get tired of this.
The conceit of MTV Unplugged is simple - get a big rock band to come in and play an acoustic set of their greatest hits. Nirvana approached the challenge differently, picking deep cuts and covers over hits, and featuring The Meat Puppets as special guests. Cobain sounds a little nervous at the start and also uses some amplification and effects in places. He passed away 5 months after this recording, lending it a poignant air, especially on Come As You Are.