Well I'm not particularly good at competitive multi-player games although I enjoy most of the ones I happen to own nonetheless. I don't mind higher deaths-than-kills ratios in games that don't take themselves too seriously like Team Fortress 2, since I tend to follow the developers' own mind set. In games like TF2 I usually keep a smile on my face most of the time, but of course if I get killed multiple times in a row the same exact way eventually it can get on my nerves a bit, but it's never really "nerd rage" material. It also depends on the game itself and how it's supposed to be played, sometimes depends on the engine (how controls respond, if there's any sort of air control for your character, how much gravity, how fast you fall or run, physics effects is any, etc). For me, a "good" Kill-Death ratio would be one that doesn't negatively impact my fun, rather than having any effects for example on either my ego or my "popularity" (be it short term or longer term, or even if it's just for the duration of a single match).
If I actually wanted to be "competitive" like I think I used to be back in the Unreal Tournament 2004 days (I loved UT99 but I sucked at it) then I would consider a "good" KDR probably something along the lines of 10 to 1. But that's very subjective. I was "content with" killing maybe a dozen players (maybe, that's the key word, never happened consistently) before dying, and I considered that "enough" and competitive, but if I was to ask other hardcore players in the match how I was doing they would have probably said that it was pretty much "normal" or not particularly significant or meaningful. I used to play a lot of capture the flag in UT 2004 and most of the time with of course some exceptions I would usually end up on the top 5 players of both teams combined for the KDR and overall score (including capturing the flag and delivering it to our base without dying).
But then again I myself am a very bad "example", even if all of this is very subjective, because even though I was "good enough" in UT 2004 that game is pretty much the only one in which I really became competitive. I did play more multiplayer games than UT 2004 of course but usually I sucked at them or I just never bothered actually trying to "get into its competitive community". I've been pretty decent with the Heavy Weapons Guy for a time back when TF2 was new (Orange Box days and until the Medic update came out) but then again being "good" at TF2, to me, never sounded very serious in itself. You know... someone telling you "oh dude yeah I RULE at TF2 I can kill like 20 before I die just once!" ... mmmm, yeah ok so... what's particularly difficult about doing that in TF2? I'm sure I've killed about as much with the HWG a few times and probably never even looked at the score board to make sure about it just because I never took the game itself very seriously. That is since I took my "performance" in TF2 with a really big grain of salt and usually laughed at my own deaths since the characters are funny and animations remind me of a Pixar movie and it's so lighthearted overall.
But, anyway, I guess that's just my own perception...
I have to say however that I usually prefer co-operation modes in multi-player games. That's probably why I spend more time playing The Last Stand (Dawn of War 2) and Mass Effect 3's multi-player lately more than I would launch Planetside 2 or Bad Company 2. Although of course to some extent you are co-operating with your own teammates in team-based games. But when I refer to co-operation I usually mean human players against A.I., because as soon as the enemy happens to be rival human players I categorize such modes and games as being "competitive" games, rather than being plainly about co-operation, even though yes I know... it is just that and as a team too. Anyway... again, my perception on games, it's quite subjective. So, "good" KD ratio? I don't have a definitive example, even for myself, what's important as I mentioned, for me, is to just happen to have a KDR that doesn't have any form of negative effects on my fun in the game. In fact if a KDR of mine was to be so low as to make me rage quit then the game itself would not be for me, rather than the KDR itself being the reason for quitting. If I have fun in a game I will probably ignore my KDR unless you bring me back about six or seven years and make me play UT 2004 again in the context of it still being new.