I have mgs hd collection on ps3, but i'm wondering, is it worth buying these games on pc?

I think the general consensus is the HD Collection is significantly superior, so perhaps not. I haven't played nor am interested in the series so I could be wrong but I think that's what I've gathered from reading reviews.

Metal Gear Solid is not a part of the HD collection though.

I personally think it's great to have the PC version of Metal Gear Solid available, but my favorite version is still the original psx version. I would recommend buying it on the playstaion store, or emulating it. The PC version is missing some effects, has lower quality audio, and doesn't have rumble, which is great to have, since the original game took advantage of rumble very well....