I am considering getting the entire set of Unreal games offered here on GOG, but after comparing prices with Steam, I'm sort of undecided...
GOG is offering Unreal Gold and UT:GOTY at $9.99 each, assuming they match Steam's prices on the individual games, Unreal II and UT2004:ECE would be priced at $9.99 and $14.99 respectively. This totals to $44.96.
Steam on the other hand offers the Unreal Deal Pack which has all four above-mentioned games AND Unreal Tournament III at $39.99.
I understand GOG is offering the games without DRM and with some extras, but as compared to the inclusion of a fairly recent and decent (i.e. not past UT calibre, but pretty good nonetheless) Unreal Tournament III and the fact that it's $5 cheaper than getting the games individually at GOG, I am finding the Steam offer more attracting.
But... despite its short period of existence, the values held by GOG really appealed to me and I really want to support them, thus the indecision...
So, I was wondering if I could get some opinions here, and maybe to get information as to whether there are plans to offer game packages over here at GOG?

My assumption is that UT2004 is going to be offered for $9.99, since all the games are being sold for $5.99 or $9.99

I think so too, but Steam's offer is still much cheaper, with the inclusion of UT3 in the deal.

All four titles will be 10$ individually, so you'll only be missing out on UT3, but not paying more. I would say skipping on UT3 is a small price to pay to get EPIC (and EA, and Ubisoft, etc.) to reconsider their stance on DRM and software piracy.
Anyway, some GOG people dropped hints that they're working on making their offerings even more attractive, which could mean bundles such as the proposed Unreal collection package. So, you could wait a week or two and see what they announce.

Actually, I would consider paying $39.96 for 4 games (GOG's Unreal offerings) compared to $39.99 for 5 games (Steam's Unreal Deal Pack) as "paying more". =P
But like you said, there are hints that GOG might make the offers more attractive, so I'll hold out a bit before buying anything.

Actually I'm not sure if you're familiar with the news or not, but Epic and Ubisoft are no longer making PC games, supposedly due to piracy.
As far as on topic: I would agree a collection would be a good thing.

Which is the stance I'm referring to that needs reconsideration.

Ah, ok, then that makes sense. I was just clarifying in case you didn't know yet :)