LA1 all the way. I like the simple, crisp colors, punchy music, and the basic strategies demanded by the single weapon.
In LA2, the dreary backgrounds actually make me depressed. I bought this game when I was twelve and came down with a cold as I started to play it. Also, the protagonist shows too much skin. The hero in the first game looks like a caveman and that's fine. The second dude looks like a sweaty, modern white guy in a loincloth. And he's vaguely doughy, like the kind of guy who works out, but still drinks too much beer.