I don't think anything is as good as Haba (except other German/European brands like Fagus, Holtzinger or Ostheimer).
I think Brio is ok, but we don't have any so I don't really know.
Melissa and Doug is made in China, and the pieces we have (beyond wooden fridge magnets) do not last. The paint flakes and chips, and the wood is not solid wood.
In general, in my experience, cheaper (especially in mass market stores) usually means lower quality. I think you have to feel the piece. I've purchased cheap wooden toys from ikea that we play hard with and are still ok-and wooden toys from small retailers that are a good deal.
I can imagine that a wooden block set from t.r.u or imaginarium would be fine, I think it depends on what the toy is.
i'm interested in this, also. I would agree that I haven't been totally impressed with the quality of M&D toys--one of the puzzles my son has split b/c it's really just layers of pressed wood glued together; and the pound-a-ball thing is way too difficult to pound--even for adults! But I do love the nesting boxes they have.
We've had problems with the quality of the wooden toys from Target and Toys R Us - frankly they're just crummy. And I've heard that the M&D quality isn't great. We're just getting HABA toys now. We don't have a lot extra for toys, so we pick what we want and save for a few toys at special occassions. I've been really pleased with all of our HABA toys.
I don't know about safety, but the M & D toys are not as durable. My twins are pretty easy on toys and the stuff still chips. However, they are widely available and affordable and I was pleased that they got a couple of them for Christmas instead of plastic battery junk.
We have a couple of Imaginarium block sets and I really like them. So far they seem better than M & D.
We don't have Brio or Haba. I have trouble finding them second-hand and they are just too expensive.