errr so which one that suppose to be best between this movies?
I don't pick single favorites, but have a few that I like. I'm also a fan of so-bad-it's-good, so I like the bad ones too.
I like "Contact".

Both the novel and the movie. What plothole?
I'm watching "Sphere" (1998) right now. It got negative reviews, but I think it's quite good. It doesn't have big fights with bug eyed monsters, but the story is loaded with genuine science fiction themes like first contact with aliens, spacetravel, timetravel, time paradox... good stuff.
Pacific Rim is a joke. Battleship is a joke. Avatar is a - admittedly nice looking - joke.
I will agree that there was an annoying character in it, but I'm curious as to who your choice is (hint: mine's not Elly Arroway).
WHAT plot hole?
I'm generally not a Matthew McConaughey fan so his presence brings
Contact down for me.
The plothole I'm talking about is the massive
deus ex eff you audience moment when the first machine is destroyed by a suicide bomber and a moment later they reveal that random effing billionaire numbnuts has built a second machine on the other side of the planet and it hasn't been mentioned before because REASONS. Okay, maybe it's not technically a plot hole, but it is inexcusable.
I remember watching and liking
Sphere and
The Abyss--I always link those two movies together despite different casting and release dates for the nautical theme. Plus I saw them within a week of each other.
I'll disagree with the upthread slamming of Avatar. I really, really enjoyed it. The gaia/interconnected web of life really, really worked from a transhumanist perspective. And I like that they right out called the plot element 'unobtainium'; no googlygook there. Or, at least, they just admitted it.
Its plot and characters were so stale, you could tell exactly what was going to happen to each character within 5 minutes of seeing them on screen. Hey, it's a hot-shot Latina pilot. She's probably going to go down in a blaze of glory. Look, scarface is probably a bad guy because he's been disfigured, and as it turns out he is. And so on.
Yeah! Thank goodness for the human race that apple (well TCP/IP really I guess, but hey they used a mac) negotiating protocols were able to communicate with that mothership's OS!
You are going to love the hacker in
The Core. I can just tell.
2001: A Space Oddyssey: One of the best shot movies of all time. Just absolutely glorious cinematography and editing. People complain about how slowly it moves, but I think the lurching pacing and drawn out scenes really do it justice. You really get a sense for the buildup of time. And the last 20 minutes are some of the most suspenseful cinema I've ever seen. You really feel the weight and terror of being an astronaut and entering the unknown during those final bedroom scenes.
I don't know if I was discussing this with you or another poster before, but I just can't get past the lack of solid character development sans one who doesn't appear until half-way through the film. The slow pace seems to only reinforce the lack of character development because I'm sitting around listening to classical movement wondering why I care about anyone on that ship as well as the monkeys.
Why are you the only one to mention Battlefield Earth?
I don't know, but that and anything MST3K panned are great for a bad scifi night. As well as anything SyFy releases.
For my money ($0), you can't get better than watching MST3K pan
Space Mutiny on youtube. It features Captain Santa Claus, First Officer Sting,
Big McLargeHuge as the action hero, the 50 year old milf-daughter love interest, and all the visuals ripped straight from the original
Battlestar Galactica.
EDIT: And I forgot the railings!
Worst, probably Plan 9 from Outerspace. Still Plan 9 is endearing, though. Sort of like an ugly dog, you just feel pity for it.
Love it.