not at all, there are many metal bands that has only one guitarist, for example black shabath, symphony x, pantera.. you don't need two gituarists to sound amazing
I could go all day long but my favs are
- Led Zeppelin
-Pink Floyd
-Jimi Hendrix Experience
-John Mayer Trio
-SRV and Double Trouble
Well they use an extra guitarist sometimes, but the main members are still only 1 guitarist.
Motorhead, if I remember correctly. Quite a few different genres that feature guitar have only one main or only one guitarist playing. If Green Day counts as Rock, then include them. RHCP and Zeppelin were notorious for only one main guitarist
Tons of punk and grind bands only feature one guitar. Hell, a lot of the time in grind, they don't even have a bassist to back them up. Converge only have one guitarist. The Fall of Troy only has one guitarist. I always really appreciated a big/good sounding band with just 4 members, better yet, a 3 piece where the front man plays an instrument.
See, the thing with Van Halen was, Sammy played Rhythm guitar a lot of the time when he was in the band, so completely, Van Halen is not just a one-guitarist band.

White Lion, yeah. They had just Vito, if I remember correctly.
If your question is what is the best grunge/punk trio, I'd point you in the direction of Motörhead - they were punk, metal, grunge, and everything else with a mean guitar just depends on the song.

If your question is what's the best band with one guitarist well shit the bed there's too many to list but you can't go wrong with any Blackmore of Malmsteen record.
Grunge is a bit iffier topic to stand for just a few bands at a time to me. Post-Grunge is even worse to quality.

I agree with Motorhead, though ^^