This summer's major artillery has taken over North American multiplexes with the mid-week launch of the action tentpole Transformers: Revenge of the Fallen which aims to become one of the top-grossing blockbusters of 2009. Michael Bay's followup to 2007's third highest-grossing film exploded on Wednesday with an early studio estimate of $60.6M including $16M from post-midnight shows on Tuesday night. Signs point to the new Autobots flick to match or exceed the all-time record for a Wednesday-to-Sunday debut which has been held for five years by Spider-Man 2 which banked $152.4M in July 2004.

Transformers rolled into 4,234 theaters on Wednesday including 169 giant and not-so-giant Imax screens which are all charging higher ticket prices which will help pump up the grosses. Paramount is looking to end its extended debut weekend at or above the level of the previous pic which opened in a slightly different manner. That hit began its opening frame with showtimes starting at 8pm on a Monday and grossed a stellar $155.4M in 6.5 days including $70.5M over the Friday-to-Sunday period and $84.9M across the 3.5-day period before the weekend.

The competitive environment is perfect for Optimus Prime. Knowing the sheer force of the pic, other studios have steered clear of opening any major action tentpoles in June leaving open seas for Fallen. In fact the top action film in the country, The Taking of Pelham 1 2 3, will only be in the single digit millions this weekend. So those looking for a high-octane summer thrill ride, especially teens now done with the school year, will have no other options. Reviews have been dismal, but don't expect them to have much of an impact. This one is critic-proof. Word-of-mouth will mean more so if first-week audiences are not too thrilled then Matrix Reloaded-like drops could follow.

Fallen kicked off what is sure to be a gargantuan debut with an eye-popping $16M+ in post-midnight sales on Tuesday night ranking third best in box office history behind The Dark Knight which bowed on a Friday last July and Star Wars Episode III which launched on a Thursday in May 2005. Knight scored $18.5M post-midnight repping 28% of its record-setting $67.2M opening day while Star Wars banked $16.9M or 34% of its $50M first day. Harry Potter and the Order of the Phoenix, which previously held the mid-week record for the biggest post-midnight debut, took in $12M which was 27% of its $44.2M opening day.

Optimus Prime in Revenge of the Fallen

If ROTF's Wednesday estimate holds, it will be the second largest opening day gross of all time after Dark Knight. Thursday grosses will tumble, possibly by more than 50%, before jumping back up on Friday for a weekend tally that will be one of the biggest of the year. Currently, X-Men Origins: Wolverine holds the mark for the year's best bow with $85.1M.

Starpower is greater for the new Megatron pic as Shia LaBeouf has become a bigger draw thanks to last summer's Indiana Jones film. He's looking to become the first actor in history to score $300M+ blockbusters over three consecutive summers. Megan Fox, who was a virtual unknown when the first Transformers hit theaters, has become one of the most talked about celebrities in the business - not for any string of hit films, but for her photogenic face which cameras love. The two actors will help bring in young females who ordinarily would not be too excited by a robot flick.

With a production budget said to be well north of $200M, Revenge of the Fallen carries a bigger price tag than its predecessor which cost $145M. The eventual global haul for the new installment stands a good chance of beating the $707M of the last one thanks to more brand awareness and an extensive worldwide publicity tour in recent weeks. Action sells overseas and Paramount wants to pick up every Euro, Pound, and Yen. Excitement is high, appeal is broad, and no other films have must-see buzz this weekend. Domestically, Transformers: Revenge of the Fallen may gross about $89M over the Friday-to-Sunday period and a jaw-dropping $171M over the full five-day debut span.

Megan Fox and Shia Labeouf in Transformers

Looking to earn a fraction of that amount is the weekend's other new wide release, My Sister's Keeper starring Cameron Diaz and Abigail Breslin based on the best-selling book. The PG-13 pic about a girl with leukemia whose younger sibling is a donor match is looking to play to a more female crowd not interested in special effects, but rather a touching tale that tugs the heartstrings. Warner Bros. will have a tough time getting audiences as moviegoers, especially in the fun summer season, do not want to spend money on depressing films. Cancer is a tough sell. The studio's marketing department was given a doozy of a flick to sell and to its credit has done a commendable job with what it has to work with. Positive reviews and good starpower will certainly help the cause. But women are likely to have a much better time with Proposal and Up and even The Hangover. Just those looking to cry will buy tickets here. My Sister's Keeper opens Friday in 2,606 theaters and could collect about $9M.

Cameron Diaz and Sofia Vassilieva in My Sister's Keeper

Sandra Bullock and Ryan Reynolds found their way to a big top spot debut last weekend with The Proposal and its core audience of older women is the quadrant least interested in the robots in disguise. That puts the Buena Vista release in a good position to play as counter-programming and register a solid second frame. A 40% decline would lead to a $20M take boosting the ten-day tally to an impressive $71M.

The Hangover will lose some of its male followers in its fourth round so a 30% drop could occur. That would give the Warner Bros. hit about $19M lifting the total to a stunning $185M. Fellow summer blockbuster Up should continue to play well with family audiences and fall by 30% as well to roughly $16.5M for a $253M cume.

Sony's buddy comedy Year One has been fading fast this week and with Transformers entering the session, its young male audience will dry up. A 55% tumble would lead to about $9M for a sum of $36M in ten days.

LAST YEAR: Two muscular debuts pumped in over $114M into the box office with Pixar's WALL•E leading the way with $63.1M followed by the Angelina Jolie actioner Wanted with $50.9M. Both became global smashes with the animated pic grossing $223.8M domestically and $535M worldwide before picking up an Oscar. Universal's R-rated flick went on to bank $134.5M from North America and $344M around the world. Rounding out the top five were holdovers Get Smart with $20.2M, Kung Fu Panda with $11.7M, and The Incredible Hulk with $9.6M.