Careful! A few more unpopular opinions are imminent.
01. Revelations 2
My most played game on Steam, largely due to Rape Mode, but I've also played through the campaign at least ten times. It has everything I wish for in an RE game, and everything is executed very well: the story, most of the characters, the locations, the gameplay... Only minor complaints concerning Claire's dullness and Ada's absence from Rape Mode, but then comes the Overseer as my favourite RE villain of all time to make up for that.
02. RE2 / REmake 2
Introducing three of my favourite characters and bringing Resident Evil to the next level, this game had a long history of constantly fighting with RE1 for the top rank on my list until Revelations 2 came along, then for the second place, but now, the second remake has officially triumphed over the first one. If only Capcom had put more effort into the A and B scenarios, and Ghost Survivors wasn't complete $hit compared to Rape Mode, it could actually have made the top of the list.
03. RE1 / REmake
The one that started it all, and the one I thought would never be dethroned, except it has actually happened twice now. Incredible atmosphere, several game modes to keep you entertained, and Twink Chris is still the hottest! Too bad the controls haven't aged quite as well as the graphics.
04. RE6
Probably the second most hated RE, but my second most played game according to Steam statistics. To me it's simply a bigger and better version of RE5, which was already pretty great in itself. A better written story, less over-the-top action, a happy ending for Piers, and a longer campaign for Ada could have placed this entry higher on my list, because it sure looked to me like it was going to be the best RE ever before it actually came out.
05. Nemesis
The first RE I ever played, it will always have a special place in my heart. Jill is awesome in this one, Nemesis is scary, and we have a sexy Latino whose accent drives the foxy ladies crazy, what else could be asked for? (I know what: A reeemaaake!)
06. RE5
The least interesting and most predictable story ever (honestly, who didn't see it coming far in advance that Bird Lady was Jill?), but still a lot of fun to play, especially with a human partner. However, unlike many other players, I never had a problem with Sheva or her AI either.
07. Revelations 1
Loved it initially, but the campaign quickly got boring after the first time. No replay value at all, Jill and Chris are duller than ever, the new characters suck, and the story isn't nearly great enough to justify being so unnecessarily convoluted. I would never have touched it again if not for Rape Mode.
08. Operation Raccoon City
The most hated game with RE in its title, but I like it, especially exploring those interesting characters and their abilities to find out what works best in which situation. Fun-wise, I would even put this above Revelations 1, but all in all, I'd say Revelations 1 is still the better game. (Sorry, Bertha! You will alway be my favourite Frau Doctor Dominatrix, you know that, right?)
09. RE4
This used to be at the bottom of my list for a long time, mainly because the original PC port was so terrible. The HD remaster finally made it playable by adding mouse support and actually displaying the correct buttons during QTEs, but the controls are still very slow, the story is still very... ugh, and as much as I like Leon in RE2, I absolutely hate him in this one. Believe me, I've tried, but I still can't understand what (almost) everyone else loves so much about RE4.
10. Zero
No idea why Rebecca and Billy are hailed as the beta couple of Resident Evil, considering that they barely interact with each other, and when they do, the writing leaves a lot to be desired. Other than that, it could have been great as a game, but no boxes = annoying item management, and many unnecessary doors = too much loading. You spend half of your time switching items around and looking at door animations, and that's not my definition of fun. Finished it twice, tried all the outfits, never again.
11. Code Veronica
Too long, too hard, too much backtracking, ugly grey fog instead of darkness, and let's not even begin to talk about that outfit Claire is wearing! One of the greatest stories and sets of characters, but the gameplay just didn't click with me, it's like someone in the development team said: "Let's take everything that made the other classics fun and crank it up to such an unbelievable degree that everything turns into a chore!" Finished it only once, and only because it's RE.
I haven't played RE7, but wouldn't even pick it up on sale, because based on what I've seen, I think it fails both as a game (for my taste, anyway) and as a Resident Evil, which can give you an approximate idea of where I'd probably put it on my list.