I honestly can't really see anyone who liked the more poppy moments of 1984 harbouring an intense dislike for 5150 (Well, bar the Roth loyalists), it's pretty much just cut from the same cloth, albeit with the pop sensibility turned up ever so slightly. Assuming you don't mind/enjoy the whole glossy, reverb-y 80s AOR (over)production, you'll be fine. OU812 I've always basically found to be its less focused little brother. Still, some quality songs to be found there.
For Unlawful Carnal Knowledge is basically just a really good, catchy hard rock record. It's much less caked in 80s synths than 5150 and OU812, so if you find that off-putting, you're in luck. Balance I find to a little too '90s for me (and frankly, boring), but I know quite a few people seem to like the darker, more serious (Mature?) direction they took with that one.
VH3 really isn't very good though, the absolutely abysmal production and mixing job essentially kills what could've potentially been some reasonably good songs. I've heard people saying that VH3 could've been better had Mitch Malloy actually stuck around in Van Halen for more than five minutes, but I disagree. Although I have to say I'll take Malloy over Gary Cherone anyday, Cherone's vocals were certainly not the weakest link on VH3.