Just play all 3, they all have their golden moments and their less than ideal scenarios.
ME1 has a really good story and some characters and their interactions/missions are quite cool albeit very short or not fun in a sense of game play. The story and main missions however are extremely interesting, with the main antagonist, Saren being more a victim than a legitimate enemy which makes fighting him really interesting. ME1's biggest let down, the game play is really really average and was the reason I almost gave up on the entire game. Combat takes some getting use to, you'll be annoyed at the ludo narrative dissonance where in which you're told to be a highly trained soldier yet for some reason your abilities in both weapon wielding (FUCK using the sniper) and power usage start off at base levels (though this is present throughout the entire game for obvious reasons) and it's not as easy to use a variety of team mates and you will probably find yourself sticking to only the same 2 throughout the game. The planet exploration is quite boring as there is very little to actually explore other than a mostly barren planet with some rocks that you can scan and some random enemies to kill (the latter only ever branching off to side quests every now and then). As for the Mako, it's okay if you only use it when the main mission tells you to, other than that using it in planet exploration is done only because it's faster than being on foot, it's controls do not work well for climbing mountains (and there are too many planets with mountainous terrains).
ME2 has the BEST squad mates out of the entire trilogy, all of them being quite useful and having really good side quests. Weapon usage at the start feels better than ME1 as you can shoot straight (and the sniper rifle is steady(but not dead steady)) and the enemies react to being hit. The games story is good and does keep the pressure high, but it's nothing special (does have some good reveals and will pull you through). Weapon selection is way worse in this one than any of the other games as you only have 2 choices for each weapon class (eg. AR/SMG with burst fire or full auto, sniper rifle with high damage or large clip) there's not weapon modification and the only way to make them better is to upgrade them through Mordin's lab. It's not so bad, but it is annoying when ME1 and 3 both give you the ability to make a unique weapon for yourself. Side missions (bar the loyalty ones) aren't really worth the effort doing or finding, you will probably find one or two squad members annoying for reasons that only work for you (I hate Tali...) and when it comes to moving around in the ship to talk to everyone you may get annoyed at having to go through so many loading screens.
ME3 has the best combat out of all the games. Shepard feels mobile and skilled (at least with weaponry) from the very start, and the addition of heavy melee attacks is quite welcome. You must remember though that this whole game does follow a third act structure, it is the conclusion to the series and thus you will spend time tying up loose ends, most of which are done really well and have a satisfying conclusion that does take into account past choices (the fate of the Krogan, Geth vs Quarian being the biggest and best examples). The leveling system was my personal favourite of the 3 games as it's not as bloated as ME1 but not as straight forward as 2, you can uniquely upgrade your abilities after the 3rd upgrade to suit your play style. Grenades are a huge plus in combat, but are by no means game winners, enemies for the first time REQUIRE you to come into battle with a team mixed of biotics, techs, and soldiers and this makes the (albeit small roster of) team mates so much more useful and makes combat interesting. However, there are missions that do suck and the reactions/attitude of some NPCs may cause you to want the Reapers to win (or at least wipe them in particular out). Though I and a decent chunk of people did enjoy or at least not get upset by the ending, I will say that many were dissapointed by it, this however should not stop you from giving the series a go.
So yeah, play all 3, don't skip the last 10 minutes and see what you think.