There's more to Kabuto than the third-person stuff (it includes an RTS mode)--and even that changes dramatically based on the character(s) you're playing/controlling, including Delphi and the giant creature Kabuto himself! Maybe you should give it another try? Use the level cheat to skip ahead if you must.
As regards Sacrifice: that sounds like something you may want to contact support about. You can also post a message on the Sacrifice forum. Be sure to include as much detail about your system as possible--a concise "it doesn't work" isn't enough to solve any problems you might be having. For what it's worth, it's a truly one-of-a-kind, excellent third person RTS.
As regards the topic: no real regrets, except maybe "Die By The Sword", which I have somehow been reluctant to install until now.

Well, this motivated me to go through my 120+ games to see which ones I should really have avoided spending my hard-earned $$ on.
Amerzone - I bought this for $9.99, and, well, it's meh. Overpriced.
UFO: Aftermath - Never could get into it. Bad UFO wannabe.
M&M 6-Pack - I'll never be able to find time to play any of these. Waste of money.
Evil Genius - For some reason I couldn't enjoy this game as much as I may have thought.
Megarace 3 - Bought this for, I think, less than $3 on a sale. Still not worth it.
Tom Clancy games - Crippled on GOG since they can't be upgraded with their expansion packs (which may not be an issue as they'll probably not be released anyway). Also, too hard, too complex, no time.
HoMM - Bought because of completionist / collectors syndrome. Never really played, an utter and complete ripoff at $9.99.
Sacred Gold - Bought to get a DRM-free version, never played it. On the other hand, never really played the disc version I own either ...
Postal 2 Complete - Doesn't work properly on my computer, isn't really that good of a game. Bought out of curiosity, was disappointed.

Well there's several I never got around to playing and bought solely on the "ooh its something (sorta) new" impulse but of the ones I've played I can only really say I regret a few.
Avent Rising is just a pile of poo which is a real shame since it had potential
I've had tech trouble with gorky 17 & interstate 76 that were so substantial that I couldn't play them, must try them on the new PC and see if that makes a difference

There's a great texture mod out or will be out soon that brings the game up to speed.

I have 35 GOGs and no regrets so far. I do chose them carefully though, so I suspect random purchases would have less satisfactory results.
Hmmmm....
Thinking about it, those 35 games have pretty much exhausted my safe choices from GOG's library.

Stay away from Gorky 17 if you have a newer Nvidia card as the game will crash on you.
Personal opinion, but stay clear of Robinson's Requiem Collection as well, you die way too often, and there is precious little information provided the user to play the game.
I have found M.A.X. + M.A.X. 2 not to be worth the money as the path finding is, well, nearly non-existent. Lots of fun to be had trying to get units to move where you need them!
Have fun.

Not that the games are bad or this is gog's fault, but I regret buying Descent 3 and Freespace 2 without having the right controller.
I bought Gabriel Knight:Sins of the Fathers and I couldn't get into it at all. Hated the voice acting, thought it was ugly, and I realized I enjoy click and point adventure games much more when they are lighthearted and funny (monkey island, sam and max).
I also regret buying Giants because of this problem here:
http://www.gog.com/en/forum/giants_citizen_kabuto/music_with_black_screen

I have only two regrets:
Blood 2: The chosen. I loved the first one and i thought this would be more of the same, it's my fault for not doing a bit of research before buying it.
Empire Earth Gold: I never got it to run, it always crashes right after the intro video. it seems to be a fairly well know, yet unsolved bug.

Same for me with EE, and PoP: SoT. Never been able to play.
Wish I bought Capitalism 1 instead of 2. Also bought JA2: Wildfire before JA2 thinking it was the main. Silly me.
XBLA marketplace holds MANY more regrets personally. Even Castle Crashers, of the rare XBLA games I can still pick up and have fun with isn't a "timeless" purchase like the games offered here.

Tex Murphy 1 + 2 (although I can't really complain since I got them for free).
Die by the Sword (disgraceful controls that ruined the game for me).
MDK 1 + 2 (Can't explain it, but there was something I really didn't like about these).
Second Sight (Same as above).

Yup Freespace 2 enjoyment comes with a joystick..

Same I found Kabuto a bit of a meh experience
But I got it for free so it was well worth the money :)

Meh... I think the only GoG I bought and then later asked myself why was Settlers 5..........
I shoulda stuck with just getting number 2......

Ground Control 1: Apparently it doesn't like running on a semi-modern system, Only got it because I enjoyed World in Conflict and figured I'd get Massive's other games.
Divine Divinity and Beyond Divinity: Expected something a bit different. And yes, I played DD past the beginning part of the story.

These are most of the GOGs I've regretted buying:
Megarace 1+2 - Never did figure out the controls.
Oddworld, Abe's Oddysee - Lazy console port.
Beyond Good & Evil - Lazy console port with crappy controls.
Shattered Steel - Has not aged well, to say the least. Also too difficult.
Pure Pinball 2.0 - It's just not good.
Port Royale 2 - Incredibly boring, and sloooooow.
Lionheart, Legacy of the Crusader - That's just an awful game.
However, I have more than 75 games from here, so it's not so bad.