No, you can't. I've had my share of experiences being burned on games that were touted as the best thing since sliced bread and then ended up being shit. No one can KNOW whether a game is good or not before the game is RELEASED.
Technically, you can't know whether or not you enjoy a game until you play it. Doesn't matter if you pre-order it or buy it 6 months later. Until you actually play it yourself, you don't know whether or not you'll like it.
And who says I haven't played it already? I've made it abundantly clear I own a PS3 and surely somebody as well versed as you in pirating PC games knows the ease with which anyone can trial anything.
In another thread, you mentioned that you bought MP3 and were "steeling yourself for disappointment." I assumed that meant you hadn't actually played it yet and weren't expecting the game to live up to the reviews and/or word of mouth.
If you believed that, you wouldn't be posting on forums. After a game is released it has enough exposure, critical and layman, for objective opinions to be formed. Not before. Everything else is just hype... especially the fevered ravings of E3 attendees presented in all their shaky-cam glory.
I don't post on forums in order to make purchasing choices. I post on forums to engage in videogame-related discussions and see how other people's opinions compare to my own.
Also, there's no such thing as an objective opinion. Opinions are inherently subjective. If an opinion were objective, it wouldn't be an opinion. It would be a fact. The fact is that only your opinion matters when it comes to your own personal entertainment. 20 million people apparently think CoD is GotY ever year but that means absolutely nothing if you don't enjoy it yourself.
As I mentioned before, if you pay attention to gaming news, interviews, media, etc, you can generally predict whether or not you'll enjoy a game by examining its mechanics. Take Splinter Cell: Conviction, for example. When I learned of the Mark & Execute mechanic, the binary shadow system and the inability to move bodies, it became clear to me that the game was going to be more of a shooter than a stealth game. The gameplay walkthroughs only added further credence to this. When the game came out, lo and behold, it was more of a shooter than a stealth game. Or take DX:HR. When I learned that it had a radar and third-person cover system, I instantly knew that I wouldn't like those elements. However, by reading interviews, I learned that the cover system was optional. Everything else I had seen and read of the game pointed towards it being good, so I was willing to overlook the radar issue. I bought the game and enjoyed it greatly.
Now I'm going to make some predictions about the games I've recently pre-ordered. I predict Darksiders 2 will be more of the same, only with more customization and loot and a larger game world. I predict Hitman: Absolution will have a mix of linear, scripted, story-driven missions and large, open-ended, sandbox missions. Probably a 40/60 ratio between them. I predict that I'll absolutely hate the Instinct mode but thankfully won't ever have to use it. I predict that the AI will probably not be very intelligent if you decide to go guns blazing, as has been the case in previous games and was shown in E3 shaky-cam footage. In regards to Far Cry 3, I expect many of the side-missions to be very linear and scripted. The game will likely have a lot of first-person cinematics with little to no interaction beyond button mashing. I predict the game will likely be too easy, especially with the new upgrade system.