I just picked up ME2, its in the mail. I do have ME but only played the first few missions and I never got around to getting back into it. I have a few questions: 
 

• Should I bother to play ME before ME2? Does it really matter that much?  
• Do I need to level all the way up? What are the benefits to this when importing your character into ME2?
• How long is ME1 (and how long is ME2)? (bonus points if you know the length with and with out side missions)

Yes.
 
And yes it does give grants to things such as money, the game experience with the default selected options as a result are boring as hell,  think there's an experience levelling bonus for importing, having imported a character depending on what level they are will affect how many resources you start with like palladium resources etc.
 
Mass Effect 1 is generally a good bit longer main storywise, and for extra missions, compared to the second, you will really notice it and what you do makes for a much better experience in the second game. It's not all hugely different though like say you launched a cruiser into the citadel council chamber as some wacky example, in mass effect 2 you'd probably only hear about it and certain NPCs won't be around because they died etc or whatever effects said example would probably cause. As opposed to a gaping hole in a building for example.

-Yes, its plot leads directly into mass effect 2. If you dont play the first game, alot of the events of the second game wont mean nearly as much. For instance if you don't play ME1 you wont know why wrex is cool. If you listen to the bombcast you know how much they love wrex. He might not even show up in your game if you dont play the first one.
-No, you do not need to level all the way up, one complete playthrough ending around level 30 something will give you a good amount of carryover benefits. Dont bother doing all the optional mako stuff either. Unless you want to, of course
-Ive heard you can beat ME1 in around 15 hours if you dont do any real sidequesting and you do NOT have to do sidequests to get a good ending like in ME2.  ME2 is alot longer. Maybe 40 hours if you take it at a leisurely pace.

Yes.

I'm halfway through a ME1 run just so I can have another game with a living Wrex.  2 of my 3 ME2 finishes have dead Wrex/council.  :(

I couldn't play the first ME at all. I didn't enjoy it. But all I did was wiki the first game so I understood what was going on and played the second. Which I totally loved oddly, just to share. :P

Yes:  Alot of enjoyment from ME2, especially if you play one right after the other, is seeing and hearing everything you did in the first game.  If I was a girl, there would be several giggle moments in ME2.  As a man, however, I only nod and grunt in acknowledgement in the manliest way possible.

 
No:  It really doesn't make a huge difference, and the amount of time you spend playing through the game twice to get a small amount of bonus resources can be made up in ME2 in an hour or two. 

If you want the full experience, meaning you land on every planet and do every sidequest, it will take you about 30 hours.  I did that because I really enjoyed the game, and I got the most giggle ( I mean manly acknowledgement) moments from doing that.  If you don't want to do that, do the main missions (obviously)  and only the "Harmless Fan" (Conrad Verner) and Admiral Kuhoku's side missions to get pretty much the full experience.  It will take you 15 hours.

Yes, for the sake of story continuity.

yes yes yes yes yes yes yes yes. for the last time yes

I did a pretty half ass run through ME before ME2. It actually drastically improved the second game. Felt like my actions were going to affect things in the future. Kind like real life, except in space.
 
There are certainly aspects that date it, but the story and characters are still head and shoulders above what most games offer to this day.

Yes, you need that save file

" I just picked up ME2, its in the mail. I do have ME but only played the first few missions and I never got around to getting back into it. I have a few questions: 
 

• Should I bother to play ME before ME2? Does it really matter that much?  
• Do I need to level all the way up? What are the benefits to this when importing your character into ME2?
• How long is ME1 (and how long is ME2)? (bonus points if you know the length with and with out side missions)

 I would like to play them in order but it depends on how much it matters and how long it will take. Thanks in advance for your opinions! "

Yes, you totally should.

Also get Mass Effect: Revelation.  You will read it in Keith David's voice.

Yes

I think you'll appreciate the continuity and the impact of choices made in 1 can effect how the story plays out in 2, subtly or directly. It just makes the game and the stroy of your Shepard that much more personal.

yes

That's crazy to start on the second one without going through the first one. You're
robbing yourself of the experience.

" I couldn't play the first ME at all. I didn't enjoy it. But all I did was wiki the first game so I understood what was going on and played the second. Which I totally loved oddly, just to share. :P "

Yes

I played through ME1 5 times when i realized how much carries over.  Very disappointing storywise on ME2

Thanks everybody! 
 
The majority of you say it is worth playing ME first so... I will play ME first :) I have at least a few days before ME2 even gets here so I will try and get through a bunch of ME over the weekend. 15 - 20 hours is long but not too bad. I have God of War 3 pre-orderd too... looks like i will wind up splitting my time between them... but its all good. Lots of fun to be had over the coming weeks.
 
Thanks again everybody! :)

" I played through ME1 5 times when i realized how much carries over.  Very disappointing storywise on ME2 "

I can't believe you are asking this - If you even so much as put the disc for  ME2 in before even finishing ME, then you deserve to have your Xbox confiscated! Why don't you just go and play Half-Life 2: Episode 2 first? But why stop there? Why not go watch Return of the Jedi first too?
 
 I think i've made my point... :)

yes

" @DuhQbnSiLo said:

" I played through ME1 5 times when i realized how much carries over.  Very disappointing storywise on ME2 "

Agreed. This impact ME1 has on 2's story in minimal at best. The characters from 1 that make an appearance in 2 are no longer integral to the plot. Importing a save is basically "neat" and nothing more.  Like somebody else suggested, a wiki would fill in for ME1 just fine. "

Most definitely: gives you a leg up statistically if you import your character, plot threads carry over and it's a pretty good game in its own right. I've seen it as cheap as $10 Canadian for a new copy, so it's very affordable.