Both ME1 and ME2 revolve around the paragon/renegade paradigm for passing persuade checks, while ME3 goes with a Reputation system that is more in line with what you are interested in. For reputation it doesn't matter whether you are more paragon or more renegade, just that you have enough points combined to pass a persuade check.
I don't know that you will "miss" content. You will just get different content. As mikefest said, the game has a great deal of replay value, whether by playing a different class, a different gender, or making different choices. This is particularly true of ME3 where all those choices you made in ME1 and ME2 come back to dramatically impact how certain story arcs play out, whether on Tuchanka or Rannoch.
That said, here is a primer on how the persuade system works in the various games and how to work around it to achieve the maximum flexibility in what dialogue choices you are able to pick:
For ME1 there is a "Charm" skill tree and an "Intimidate" skill tree. To pass persuade checks you need to invest points into these skill trees. From an efficiency perspective it makes most sense to only invest in one of those skill trees and use your other points to invest in combat related skills. Through your dialogue choices and your actions you can earn up to 4 free Charm points and 4 free Intimidate points per playthrough with a character. You get 1 free Charm and 1 free Intimidate when you become a Spectre. You get 1 free Charm point when you fill up 10% of the paragon meter. You get another 1 free Charm point when you fill up 25% of the paragon meter. And you get 1 free Charm point when you fill up 75% (?) of the paragon meter. It works the same way for Intimidate points, except the percentages are based on how much of the Renegade meter are filled.
There are ways to glitch up your paragon and renegade points even on the console so that you can earn those free Charm and Intimidate points. A very easy way to glitch up your paragon score, and thus max out the number of free Charm points you earn is by doing a side quest on the planet Eletania. You are tasked with finding a data module that a pyjack has stolen. You have to go searching for the Pyjack that stole the thing. If you do not kill any Pyjacks before finding the one that has the data module, then you use a save/reload exploit to pump up you paragon score. Here is an example.
There is another way to glitch up both your renegade and paragon scores to get those free Charm and Intimidate scores. For this one to work, however, you need to already have at least 5 Charm and/or 5 Intimidate points. This glitch involves repeatedly talking to the same NPC and repeating the same dialogue option over and over until you have gotten you paragon/renegade score up enough to earn the points you want. Here is an example of the glitch itself, though you may wish to watch the entire video in order to get the context for using this glitch.
For ME1, when you do a new game plus (start a new game with a character that has already completed the game at least once) you carry over all your skills that you had in your previous playthrough(s) including any Charm and/or Intimidate points you earned/invested in. For my playthroughs on youtube I start out ME1 with new game plus characters specifically because I want the freedom to choose whatever dialogue option I feel is appropriate for the situation and by using a new game plus I can carry over the Charm/Intimidate points from previous playthroughs without having spent any points myself, just those points I earned for free. So, for instance, for my Katrina Shepard playthrough I ran Katrina through the game twice in order to earn 8 free Charm and 8 free Intimidate points. I doubt you would want to do this, but for my purposes it is important that I be able to take whatever dialogue option I feel is appropriate for the situation and the character, and not because of game mechanics.
For ME2 the persuade system is rather opaque. You have paragon and renegade meters, but they actually are misleading and you should not pay attention to them. To pass persuade checks in ME2 each check requires that you are either x% paragon or y% renegade. Sometimes the percentage required is very high, sometimes it is not so high. It will also depend on whether it is an intimidate or charm option. For some persuade checks the charm option (blue) requires a low percentage while the intimidate (red) option requires a high percentage. For others, the charm option may require a high percentage, while the intimidate option may require a low percentage.
How are these percentages calculated? Every time you enter some new area/run some mission, there will be a total number of paragon points that can be earned (p), and a total number of renegade points that can be earned ( r). Let's say you land on Omega, the first hub world you will probably go to. Let's say there are a total of 200 paragon points that could be earned here and 150 renegade points that could be earned here based on the dialogue choices you make. Now let's say you earn 100 paragon points and 50 renegade points. (And you missed out on a number of points because you didn't talk to certain people or picked a neutral option.) Your paragon percentage is now 50%, and your renegade percentage is 33%. Now let's say you are presented with a dialogue where you can persuade someone. The charm option requires that you be 40% paragon and intimidate option requires that you be 35% renegade. You will be able to use the charm option (blue) because your paragon percentage is 50% which is greater than the 40% required, but you will not be able to use the intimidate option (red) because your renegade percentage is 33% which is less than the 35% required.
As you travel to more and more places and run more and more missions, the total number of paragon and renegade points you could potentially earn keeps growing and growing, but the likelihood of you earning all the points available is rather low, meaning as the game progresses it becomes increasingly harder to pass persuade checks.
For this reason, it is recommended that you 1) try to get to difficult persuade checks early in a game, and 2) import as many paragon and renegade points from ME1 as possible. You can import up to 190 paragon points and 190 renegade points from ME1. Using the above example, a character that imported 190 renegade and 190 paragon points would start out - before even talking to anyone - at 95% paragon and 126% renegade, meaning they could pass any persuade check imaginable. For an experienced player who understands how the system works it is entirely possible to play a character that is 50% paragon and 50% renegade and pass all the persuade checks in ME2.
For ME3 life got vastly simpler. Simply talk to people and do quests and your reputation will increase. It doesn't matter if you are paragon or renegade or 50/50. With enough reputation (and reputation is very easy to accumulate) you can pass any persuade check.
For ME1, my solution is to go with a new game plus and exploit the two glitches mentioned above so that I can pass any persuade check I feel are appropriate.
Depending on how you end up liking the game, however, there comes a point where you should find out happens when you don't pick one of the persuade options. Almost everyone is initially drawn to using either the red or blue dialogue option. They sit there screaming at you "pick the 'I win' option!!!" And who doesn't want to win? But there comes a point, hopefully, when you decide, "you know what, I am curious what happens if I don't pick the 'I win' option." Doing a non-persuade run through the series can open all kinds of new content, some of which you may find you like even more than the persuade options.